General Science #12 | Study Material::General Studies | IAS Help

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CHEMISTRY: SOAPS AND DETERGENTS

About soaps

  • Soaps are anionic surfactants used for washing and cleaning. Surfactants are wetting agents that lower the surface tension of a liquid
  • Soaps consist of sodium or potassium salts of fatty acids.
  • They are obtained by reacting common oils or fats with a strong alkaline solution
  • The earliest recorded evidence for use of soap is from Babylon c. 2800 BC

Mode of action

  • Soap molecules have both a hydrophilic end and a hydrophobic end
  • The hydrophilic end dissolves in water, while the hydrophobic end dissolves dirt and oil molecules
  • As a result, although water and oil don’t mix, soaps allow oil to dissolve in water, allowing them to be rinsed away
  • Thus, soaps allow water to remove normally insoluble matter by emulsification

Detergents

  • Detergents are surfactants other than soap
  • Detergents are commonly used as industrial soaps, due to their heavy duty grease removal capabilities
  • Soaps differs from detergents in that in the case of former, excess of fat is used to consume the alkali and the glycerine is not removed, leaving a naturally moisturising soap
  • In general detergents are substances that have cleaning properties. By definition, even water is a detergent

BIOLOGY: NUTRITION

Overview

  • Nutrition is the supply to cells and organisms, of the materials necessary to support life
  • Many common health problems can be prevented by a healthy diet
  • A poor diet can have injurious impact on health, leading to problems such as scurvy, beriberi and kwashiorkor
  • A healthy diet can also significantly prevent and mitigate systemic diseases like cardiovascular disease, diabetes and osteoporosis
  • Eating a wide variety of fresh, unprocessed food has proven favourable compared to monotonous diets of processed food
  • Consumption of whole plant foods slows digestion, allows better absorption and a more favourable balance of nutrients

Nutrients

  • There are six major classes of nutrients: carbohydrates, fats, minerals, proteins, vitamins and water
  • These can be classified into
    • Macronutrients: nutrients needed in large quantities. These include carbohydrates, fats, proteins and water. Fibre is another macronutrient whose functions have not been fully understood
    • Micronutrients: nutrients needed in smaller quantities. These include minerals and vitamins. Antioxidants and phytochemicals are micronutrients as well, but their functions are not well understood
  • Most foods contain a mixture of nutrients
  • Some nutrients may be stored internally (eg. Fat soluble Vitamins) while others are required more or less continuously

Carbohydrates

  • Carbohydrates are sugars, and are classified as monosaccharides, disaccharides or polysaccharides depending on the number of monomer (sugar) units they contain
  • Carbohydrates constitute a large part of foods such as rice, noodles, bread and other grain based products
  • In general, simple saccharides are easier to digest and absorb than polysaccharides
  • Since they are absorbed more quickly, simple carbohydrates lead to elevated levels of blood glucose

Fibre

  • Dietary fibre is a carbohydrate (polysaccharide) that is incompletely absorbed in humans and some animals
  • Like all carbohydrates, when metabolised it produces energy
  • However, it does not contribute much energy due to limitations on its absorbability and digestion
  • Dietary fibre consists mainly of cellulose, a polysaccharide that is indigestible in humans
  • Whole grains, fruits and vegetables are good sources of fibre
  • Fibre provides bulk to intestinal contents and stimulates peristalsis – the rhythmic muscular contractions of the intestines that moves digesta along the digestive tract
  • For these reasons, fibre is important for digestive health. It helps alleviate constipation and diarrhoea and is said to reduce colon cancer

Fats

  • Fat consists of fatty acids bonded to glycerol. Fatty acids are carboxylic acids that contain long chains of carbon and hydrogen atoms
  • They are typically found as triglycerides
  • Fats are classified as
    • Saturated fats: have all the carbon atoms in the fatty acid chains bonded to hydrogen atoms
    • Unsaturated fats: have some carbon atoms double bonded to themselves, thereby have fewer hydrogen atoms
  • Studies have shown that unsaturated fats are preferable to saturated fats in terms of health effects
  • Saturated fats are usually solids at room temperature (eg butter) while unsaturated fats are liquids at room temperature (eg olive oil)
  • Trans fats are a type of unsaturated fat with trans-isomer bonds. These are rare in nature and usually created by an industrial process called hydrogenation. Trans fats are harmful to health (coronary heart disease) and their use is to be avoided

Proteins

  • Proteins are the basis of many animal body structures and form enzymes that control chemical reactions in the body
  • Proteins are composed of amino acids, which contain nitrogen atoms
  • The body requires amino acids to produce new proteins and replace damaged proteins
  • Since the body cannot store protein, amino acids must be present in the daily diet
  • Diet with adequate proteins is especially important during early development and maturation, pregnancy, lactation or injury
  • A complete protein source is one that contains all essential amino acids
  • Sources of protein include meat, tofu, soy, eggs, grains, legumes and dairy products
  • A few amino acids can be converted into glucose for energy (called gluconeogenesis). This process mainly happens only during starvation

Minerals

  • Dietary minerals are the chemical components required by living organisms other than the four elements carbon, oxygen, nitrogen, hydrogen that are present in nearly all organic molecules
  • Dietary minerals include some metals as well (sodium, potassium) which are usually found in ionic state
  • Minerals are recommended to be supplied in the daily diet
  • Most famous dietary mineral is iodine (added to salt) which prevents goitre
  • Macrominerals (required more than 200 mg/day) include
    • Calcium: electrolyte, also needed for structural growth (teeth, bones)
    • Chlorine: electrolyte
    • Magnesium: required for processing ATP (energy)
    • Phosphorous: required component of bones, essential for energy processing
    • Potassium: electrolyte (heart and nerve health)
    • Sodium: common electrolyte, needed in large quantities. Most common source is common salt. Excess sodium depletes calcium and magnesium leading to high BP an osteoporosis
    • Sulphur: essential for certain amino acids and proteins
  • In addition to the macrominerals, many other minerals are required in trace amounts. These include cobalt, copper, chromium, iodine, iron, manganese, molybdenum, nickel, selenium, vanadium, zinc

Vitamins

  • A vitamin is an organic compound required as a nutrient in tiny amounts by an organism
  • A compound is called a vitamin when it cannot be synthesised in sufficient amounts by an organism, and must be obtained from the diet
  • Thus, the term “vitamin” is conditional both on the circumstance and the organism. For instance ascorbic acid is termed Vitamin C for some organisms but not for others, and Vitamins D and K are required in the human diet only under certain circumstances
  • Vitamins must be supplied in the diet (except Vitamin D, which can be synthesised by the skin in the presence of UV radiation)
  • Fresh fruits and vegetables are good sources of vitamins
  • Vitamin deficiencies may results in diseases like goitre, scurvy, osteoporosis, impaired immune system etc
  • Excess of some vitamins can also be dangerous: excess Vitamin A can cause jaundice, nausea, blurry vision, vomiting, muscle pain etc

Water

  • About 70% of non-fat mass of the body is water
  • To function properly, the body requires between one and seven litres of water every day
  • It is recommended that daily water intake for an adult male be 3.7 l and for females be 2.7. However, these requirements vary with climate, activity level and other factor
  • Too little water can lead to dehydration
  • Too much water can lead to water intoxication, a potentially fatal disturbance to the brain. However, this is very rare in normal humans and usually only occurs during water drinking contests or intense bouts of exercises when electrolytes are not replenished

Malnutrition

Nutrients Deficiency Excess
Carbohydrates Low energy Diabetes, obesity
Fats None Cardiovascular disease, obesity
Cholesterol none Cardiovascular disease
Protein Kwashiorkor

(edema, anorexia, inadequate growth)

Rabbit starvation (diarrhoea, headache, low BP, low heart rate

Discomfort/hunger that can only be satisfied by eating fats and carbohydrates
Sodium Hyponatremia

(electrolyte imbalance)

 Hypernatremia, hypertension
Iron Anaemia Cirrhosis (chronic liver disease), heart disease
Iodine Goitre, hypothyroidism Iodine toxicity
Vitamin A Night blindness, xeropthalmia (dry eyes) Hypervitaminosis A (birth defects, liver problems, osteoporosis)
Vitamin B1 Beri-beri
Vitamin B2 Cracking of skin
Vitamin B12 Pernicious anaemia
Niacin (Vitamin B3) Pellagra (diarrhoea, dermatitis, dementia, death) Dyspepsia (indigestion), cardiac arrhythmias
Vitamin C Scurvy Diarrhoea
Vitamin D Rickets Hypervitaminosis D (dehydration, vomiting, constipation)
Vitamin E Nervous disorders Hypervitaminosis E (anticoagulant)
Vitamin K Haemorrhage
Calcium Osteoporosis Fatigue, vomiting, depression, cardiac arrhythmias
Magnesium Hypertension Weakness, nausea, vomiting
Potassium Hypokalaemia, cardiac arrhythmias Hyperkalaemia, palpitations

LAST WEEK: ENVIRONMENTAL CHEMISTRY, VACCINES
~~~~~
NEXT WEEK: TBD

2 February 2010 | Tags: | 1 Comment »

General Science #11 | Study Material::General Studies | IAS Help

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  General Science #11 (319.6 KiB, 10,893 hits)

CHEMISTRY: ENVIRONMENTAL CHEMISTRY

Overview

  • Environmental chemistry is the study of chemical and biochemical phenomena that occur in natural places
  • Environmental chemistry is used to detect and identify the nature and source of pollutants, including
    • Heavy metal contamination of land by industry. These can transported to water bodies and taken up ingested by living organisms
    • Nutrients leaching from agricultural land into water sources
    • Urban pollutants runoff. Typical pollutants include petrol and other fuel, metals, nutrients and sediments
  • Common environmental phenomena arising out of contamination include acid rain, soil salination and ocean acidification
WATER QUALITY PARAMETERS
  • Dissolved Oxygen (Oxygen Saturation)
    • It is a relative measure of the amount of oxygen dissolved in water.
    • Supersaturation (excess of oxygen) can be harmful to organisms and also cause decompression sickness
    • It is expressed in mg/l
  • Chemical Oxygen Demand (COD)
    • COD is used to indirectly measure the amount of organic compounds in water
    • It is expressed in mg/l, which indicates the amount of oxygen consumed per litre of water
  • Biochemical Oxygen Demand (BOD)
    • BOD measures the rate of uptake of oxygen by microorganisms in water
    • BOD is measured at a temperature of 20 C and over a period of 5 days in the dark
    • BOD is widely used to determine the threshold at which treated wastewater can be re-introduced into the environment
    • Pristine rivers have a BOD of below 1 mg/l. Municipal sewage treated effectively by a three-stage process would have BOD of 20 mg/l or less
  • Total Dissolved Solids (TDS)
    • TDS is a measure of combined content of all inorganic and organic substances contained in a liquid
    • TDS is generally not considered a primary pollutant, but is used to indicate the aesthetic characteristics of drinking water
    • High TDS levels generally indicate hard water
    • Drinking water is expected to have a TDS of 100 mg/l or less
    • TDS is different from TSS (Total Suspended Solids). The former are those solids that are small enough to pass through a filter of size 2 um, while the latter are those solids that cannot pass through
ENVIRONMENTAL POLLUTION PHENOMENA

Acid rain

  • Acid rain is form of rain that is unusually acidic i.e. has low pH
  • Acid rain is mostly caused by emission of sulphur, nitrogen and carbon which react with water molecules in the atmosphere to produce acids
  • The biggest human activity causes of acid rain include coal-based power plants, factories and automobile emissions
  • It can also be caused by natural phenomena such as
    • lightning strikes (which splits nitrogen compounds)
    • volcanic eruptions (which release large quantities of sulphur dioxide)
  • Natural (unpolluted) rain is slightly acidic with pH of 5.2 due to the reaction of carbon dioxide with water to produce carbonic acid
  • Acid rain has many adverse effects including
    • Damage to aquatic animals
    • Damage to soil chemistry by killing off essential microbes
    • Loss of forests and vegetation
    • Human illnesses such as cancer, asthma and other diseases
    • Damage to buildings and historical monuments (esp. those made of limestone and marble)

Ocean acidification

  • Ocean acidification is the continuing phenomenon of decreasing pH in the world’s oceans
  • Between 1751 and 1994, ocean pH is estimated to have decreased from 8.179 to 8.104 (decrease of 0.075). Ocean pH is expected to decrease by a further 0.3-0.5 by 2100
  • This acidification is mainly the result of uptake of carbon dioxide from the atmosphere. The world’s oceans naturally absorb carbon dioxide from the atmosphere, indirectly mitigating climate change
  • Ocean acidification adversely affects marine organisms especially calcifying organisms like corals, crustaceans and molluscs, and also affects other organisms by entering the food chain

Soli salination

  • Salt affected soils are caused by excess accumulation of salts at the soil surface
  • Salt can be transported to the soil surface by capillary action from salt-laden water tables, or by human activity
  • Increasing soil salinity adversely affects soil quality and vegetation
  • Human activities that increase soil salinity include
    • Land clearing
    • Aquaculture activities (shrimp farms etc)
    • Irrigation (over a period time causes deposition of salts)
  • The adverse effects of salination include
    • loss of soil fertility
    • damage to infrastructure (such as roads etc)
    • damage to plant growth and yield
    • deterioration of underground water quality
    • soil erosion
COMMON ENVIRONMENTAL TOXINS
  1. Chlorofluorocarbons
    1. They are organic compounds that contain carbon, chlorine and fluorine
    2. Examples of CFCs include Freon, Teflon
    3. CFCs have been widely used as refrigerants, propellants (in aerosols) and solvents
    4. The use of CFCs has been banned under the Montreal Protocol due to their adverse effect on the ozone layer
  2. Endocrine disruptors
    1. Endocrine disruptors are substances that affect the function of natural hormones in the body
    2. Food is the main source of exposure to endocrine disruptors
    3. There are five main types of endocrine disruptors:
      1. DDT
      2. Polychlorinated biphenyls
      3. Bisphenol A
      4. Polybrominated diphenyl ethers
      5. Pthalates
  3. DDT
    1. Dichlorodiphenyltrichloroethane (DDT) is one of the most well-known synthetic pesticides
    2. DDT is one of the most effective and simple to deploy pesticides, especially to fight mosquitoes that cause malaria and typhus
    3. DDT has significant adverse effect on aquatic life, insects and humans (esp. diabetes and reproductive disorders)
    4. It is a significant reproductive toxicant for certain bird species, and is a major reason for the decline of the bald eagle, brown pelican peregrine falcon and osprey. This is the main reason DDT use has been banned
    5. The use of DDT for agricultural use has been banned under the Stockholm Convention, however it can still be used for disease vector control (mosquito eradication)
  4. Polychlorinated biphenyls (PCBs)
    1. PCBs are a class of industrial compounds
    2. They are used mainly as industrial coolants and lubricants
    3. Exposure to PCBs increases the risk of skin cancer, brain cancer and liver cancer. Additionally it also increases childhood obesity and the risk of developing diabetes
    4. The use of PCBs was banned in 1977
  5. Bisphenol A (BPA)
    1. BPA is an organic compound with two functional phenol groups
    2. BPA is used as a building block of several important plastics and plastic additives
    3. It is found commonly in water bottles, plastic food containers and the lining of infant formula cans
    4. The use of BPA has been linked to diabetes, mammary and prostrate cancers, reproductive problems, obesity and neurological disorders
    5. BPA use has not been banned
  6. Polybrominated diphenyl ethers (PBDE)
    1. PBDEs are a class of compounds used as flame retardants
    2. They are used commonly in televisions, computers, electronics, carpets, bedding, clothing car components etc
    3. PBDEs have the potential to affect thyroid balance, and contribute to a variety of neurological and developmental disorders including learning disabilities and low intelligence
    4. Many of the most common PBDEs were banned by the European Union in 2006
  7. Phthalates
    1. Phthalates are esters of phthalic acid
    2. They are mainly used as plasticisers to soften polyvinyl chloride (PVC)
    3. Phthalates are found in soft toys, flooring, medical equipment, cosmetics and air fresheners
    4. Phthalates have been shown to have adverse effects on the male reproductive system
    5. The EU and the US have begun phasing out widespread use of phthalates
  8. Dioxins
    1. Polychlorinated dibenzodioxins (PCDDs) are a group of polyhalogenatated compounds
    2. The main sources of Dioxins include
      1. By-products in the manufacture of organochlorides
      2. in the incineration of chlorine containing substances (like PVC)
      3. bleaching of paper
      4. natural sources like volcanoes and forest fires
    3. Dioxins accumulate and build up in the food chain (bioaccumulation)
    4. Health effects of dioxins include
      1. Severe form of acne called chloracne
      2. Abnormalities in teeth enamel of children
      3. Nervous system pathology
      4. Thyroid disorders
      5. Diabetes
      6. Damage to immune system
    5. Exposure to dioxins has been shown to affect the ratio of male to female births, such that more females are born than males

BIOLOGY: VACCINES

Overview

  • A vaccine is a biological preparation that improves immunity to a particular disease
  • Vaccines were first used by Edward Jenner (England) in the 1770s to inoculate against small pox using the cow pox microbe
  • Vaccines have resulted in the eradication of small pox, one of the most contagious and deadly diseases known to man
  • Other diseases like polio, measles, mumps, typhoid etc are have been significantly reduced. Currently, polio is prevalent in only four countries: Afghanistan, Pakistan, Nigeria and India

    Mechanism of action

  • A vaccine is usually made from a weakened or dead form of the microbe that it is intended to fight
  • It stimulates the body’s immune system to recognise the microbe as foreign, and destroy it and remember it
  • When the same microbe re-appears later, the immune system easily recognises and destroys it
  • When the body recognises the virulent microbe attack, it
    • Neutralises the target microbe before it can enter body cells
    • Destroys infected cells before the microbe can spread to other cells and multiply

Types of vaccines

  • Killed vaccines: these are vaccines that contain micro-organisms that have been killed using chemicals or heat. Eg: influenza, cholera, bubonic plague, polio, hepatitis A
  • Attenuated vaccines: these contain live attenuated (numerous) micro-organisms. These are usually live viruses that have been cultivated under conditions which disable their virulent properties, or use closely-related by less dangerous micro-organisms. These vaccines provide more durable immune response and are preferred type for healthy adults. Eg: yellow fever, measles, rubella, mumps, typhoid
  • Toxoid vaccines: inactivated toxic compounds that cause illness. Eg: tetanus, diphtheria
  • Subunit vaccines: these use protein subunits instead of the entire micro-organism as a vaccine. Eg: Hepatitis B vaccine (which uses only surface proteins), Human Papilloma Virus (HPV) vaccine (which uses subunits of influenza virus)

Effectiveness of vaccines

  • Vaccines do not guarantee complete protection from a disease
  • This could be due to
    • Host’s immune system may not respond adequately
    • Host may have lowered immunity (such as due to diabetes, HIV, steroid use etc)
    • Host may not have a B cell capable of producing antibodies to that particular antigen
  • The efficacy of a vaccine depends on a number of factors
    • The disease itself
    • The strain of vaccine
    • Following the schedule of vaccinations
    • Individual host factors
    • Genetic and ethnic predisposition
  • Most vaccines use adjuvants to boost immune system response. Adjuvants are compounds added to the vaccine that increase the immune response, without having any specific antigenic effect by themselves.
  • Aluminum salts like aluminium phosphate and aluminium hydroxide are the most common adjuvants used

List of important vaccines

Vaccine Disease Type Notes
Anthrax vaccine Anthrax Protein subunit
Bacillus Calmette-Guerin (BCG) Tuberculosis Live bacteria
DTP Diphtheria

Pertussis (whoopoing cough)

Tetanus

Gardasil

(Human Papilloma Virus (HPV))

 Cervical cancer Protein subunit
Polio vaccine Polio Killed/inactivated Polio is prevalent only in humans

Currently polio has been eradicated from all countries except Afghanistan, Pakistan, Nigeria and India
MMR Measles

Mumps

Rubella

Meningococcal vaccine Meningococcus
Rabies vaccine Rabies Attenuated
Yellow fever vaccine Yellow fever Attenuated

LAST WEEK: IMAGING, MEDICINES
~~~~~
NEXT WEEK: SOAPS/DETERGENTS, NUTRITION

26 January 2010 | Tags: , | 1 Comment »

General Science #10 | Study Material::General Studies | IAS Help

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  General Science #10 (310.0 KiB, 5,911 hits)

PHYSICS: NON-INVASIVE IMAGING

Overview

  • Medical imaging is the technique and process used to create images of the human body for medical purposes
  • Non-invasive imaging is the method of producing images of internal tissues without surgical procedures
  • Non invasive imaging techniques can be used to produce anatomical assessment of tissues (such as X-rays) as well as functional assessments (such as MRI)
  • As a discipline, it includes radiology, nuclear medicine, endoscopy, thermography etc
  • Non-invasive imaging is a vast field with differing technologies such as X-rays, tomography, MRI etc
  • Non-invasive imaging provide highly valuable diagnostic tools for diagnosing and treating varied ailments such as cancer, fractures, etc
  • Imaging technologies can be broadly classified into two categories
    • Anatomical imaging modalities: these imaging techniques provide information on the anatomy i.e. the physical structure of the organ/tissue under study
    • Functional imaging modalities: these imaging techniques provide information on the physiological functioning of the organ/tissue under study

X-RAYS

  • X-rays were discovered by Wilhem Conrad Rontgen (Germany) in 1895. He won the Nobel in Physics 1901
  • Radiography is the imaging process that uses X-rays to capture images
  • In conventional radiography, X-rays from a X-ray tube pass through the patient and are captured by an X-ray sensitive film screen
  • Nowadays, digital radiography (DR) is becoming popular, in which x-rays strike an array of sensors that convert the signal to digital mode and displays the images on a computer screen
  • X-rays are the preferred diagnostic tool for studying lungs, heart and skeleton (including fractures) due to their simplicity, available and low cost
  • X-rays is an anatomical imaging technology

Fluoroscopy

  • Fluoroscopy is used to obtain real time moving images of the internal structures
  • Fluoroscope systems consist of an X-ray source and a fluorescent screen connected to a closed circuit TV. The patient is position between the source and the screen
  • Fluoroscopes use low x-ray radiation doses
  • Fluoroscopy also involves use of radiocontrast agents that increase the contrast of a specific tissue w.r.t. surrounding tissues by strongly absorbing or scattering the x-rays
  • The radiocontrast agents enable visualization of dynamic processes such as peristalsis in the digestive tract of blood flow in arteries and veins
  • Commonly used contrast agents include Barium and Iodine. These may be administered orally or rectally or injected into the blood stream
  • Used mainly for investigating gastrointestinal functions, orthopaedic surgery and urological surgery
  • Fluoroscopy is a functional imaging technology

Computed Tomography (CT)

  • Computed Tomography uses X-rays in conjunction with software algorithms to image the body
  • CT generates a three-dimensional image of an object using a large series of X-ray images taken around a single axis of rotation
  • CT produces a volume data which can be manipulated in order to demonstrate various body functions
  • Compared to traditional radiography, CT produces 3d information and has much higher contrast and resolution, but also uses much higher doses of radiation
  • CT scanners were first developed by Sir Godfrey Hounsfield (Britain) in 1972. He won Nobel in Medicine in 1979
  • CT is used primarily for detecting cerebral haemorrhage, pulmonary embolism, aortic dissection, appendicitis and kidney stones
  • CT is an anatomical imaging technology

Ultrasound

  • Ultrasound was first developed for medical use by John Wild (Britain) in 1949
  • Ultrasonography uses ultrasound (high frequency sound waves) to visualize soft tissues in the body in real time
  • Ultrasound does not involve any ionizing radiation, hence it considered safer than X-rays or CT and is used for obstetrical imaging
  • Ultrasound is limited by its inability to image through air or bone, and by the skill of the examiner
  • Ultrasound is used primarily to study the development of foetus
  • A variant of ultrasound, the colour flow Doppler ultrasound is used in cardiology for diagnosing peripheral vascular disease
  • Ultrasound is a functional imaging technology

Magnetic Resonance Imaging (MRI)

  • MRI was invented by Paul Lauterbur (USA) and Sir Peter Mansfield (Britain) in the 1970s. They won Nobel in Medicine in 2003
  • MRI uses strong magnetic fields to align atomic nuclei within body tissues, and then uses a radio signal to disturb this alignment and observes the signals generated as the atoms return to their original states
  • The working principle of MRI is called Nuclear Magnetic Resonance (NMR)
  • MRI scans give the best soft tissue contrast of all imaging modalities
  • MRI does not use any ionizing radiation. However, it does use powerful magnetic fields
  • A variant of MRI called Functional MRI measures signal changes in the brain due to neural activity
  • MRI is used primarily for neurological (brain), musculoskeletal, cardiovascular and oncological (cancer) imaging
  • MRI is an anatomical imaging technology

Nuclear medicine

  • Nuclear medicine uses radioactive isotopes and the principle of radioactive decay to study body functions
  • Nuclear medicine involves the administration into the patients of radio-pharmaceuticals.
    Radio-pharmaceuticals are substances with affinity for certain body tissues that have been labelled with radioactive tracers (called radio-nuclides)
  • The radio-pharmaceuticals administered into the body emit radiation which is detected and converted into images.
  • The radio-pharmaceuticals, once administered, localise (i.e. attach) to specific organs or cell receptors, meaning those particular organs or cells can be studied in isolation
  • Commonly used tracers include Technetium, iodine, gallium and thalium
  • Nuclear medicine is used mainly to study the heart, lungs, thyroid, liver and gallbladder
  • Nuclear medicine mainly provides information about the physiological function of these tissues
  • Since the radio isotopes decay over a period a time, they do not pose a significant threat to normal human functioning
  • Nuclear medicine is a functional imaging technology

Positron Emission Tomography (PET)

  • PET uses nuclear medicines to produce three dimensional images
  • The PET system detects gamma rays emitted by positron emitting radio-nuclides. Images of the nuclide concentration are reconstructed in 3d by computer algorithms
  • PET is a functional imaging technology
  • PET is often combined with CT and MRI scans, enabling both anatomical and functional imaging simultaneously
  • PET was first developed by David Kuhl (USA) and Roy Edwards (USA) in the 1950s
  • PET is mainly used in oncology (cancer) and neurology (especially dementias)
  • A variant of PET, called Single Positron Emission Computed Tomography (SPECT) detects gamma rays emitted directly by the radio-nuclides

CHEMISTRY: MEDICINAL CHEMISTRY

  • Medicinal chemistry involves the design, synthesis and development of pharmaceutical drugs
  • Compounds used as medicines are overwhelmingly organic compounds including small molecules and biopolymers. However, some inorganic compounds and metals have been found to have medicinal properties as well

Classes of drugs

Class of drug Application Example Notes
Antipyretics Reduce body temperature Aspirin, paracetamol (acetaminophen) Antipyretics cause the hypothalamus to override an increase in temperature

Taking antipyretics in empty stomach can cause ulcer
Analgesics Pain relief Paracetamol

Non steroidal anti inflammatory drugs (NSAIDS)

Morphine

 Some antipyretics act as analgesics as well

Some narcotics (heroin, morphine, marijuana) can also act as analgesics
Tranquilizers Induce sedation Barbiturates, antihistamines Sedatives cause sleep, poor judgement, slow reflexes

Excessive use can cause unconsciousness and even death
Antiseptics Reduce possibility of infection Boric acid, hydrogen peroxide, iodine Antiseptics are applied externally to living tissues

Antiseptics also reduce body odour caused due to bacterial decomposition

They are used in breath freshners and deodorants
Antibiotics Kill bacteria Penicillin, gramicidin, amoxicillin, streptomycin An antibiotic is defined as a substance produced by a microorganism that kills other microorganisms

Antibiotics are considered life-saving drugs
Diuretics Increases rate of urination Amiloride, triamterene
Vasodilators Widen blood vessels Histamine, nitric oxide Decrease blood pressure

Increase blood flow
Vasoconstrictors Narrow blood vessels

Staunch blood loss due to haemorrhage

Antihistamines, cocaine, LSD, caffeine Increase blood pressure

Decrease blood flow

Make skin look paler because less blood reaches the skin
Anaesthetics Cause loss of sensation Cocaine, nitrous oxide, halothane General anaesthetics cause a loss of consciousness

Local anaesthetics cause loss of sensation in a specific part of the body
Antifungals Fungal diseases like ringworm, athlete’s foot, meningitis Ketoconazole, benzoic acid, neem seed oil, tea tree oil Since both fungi and human cells are eukaryotes, the possibility of side effects is higher than in anti-bacterial drugs (like antibiotics)
Antivirals

(Antiretrovirals)

 Inhibit growth of virus Zedovudine, lamivudine Unlike antibiotics, antiviral drugs do not destroy target microbes but only inhibit their growth

Designing antiviral drugs is difficult because virus use host’s cells to replicate

Some virus, like influenza and HIV, mutate rapidly which means they can be treated with antivirals only and not be prevented by vaccines

Antiretrovirals are a subclass of antivirals that treat retroviruses such as HIV

Some important common drugs

Drug Classification Application Notes
Penicillin Antibiotic Syphilis, staphylococcal infections (food poisoning) Narrow spectrum antibiotic

(treats only a narrow range of diseases)
Zedovudine Antiviral HIV
Lamivudine Antiviral Hepatitis B
Streptomycin Antibiotic Tuberculosis
Erythromycin Antibiotic Respiratory tract infections
Ciprofloxacin Antibiotic Urinary tract infections, common pneumonia, myoplasmal infections Broad spectrum antibiotic
Amoxicillin Antibiotic Wide range of infections Broad spectrum
Tetracycline Antibiotic Cholera
Chloroquine Antibiotic Malaria
Aspirin Analgesic, Antipyretic Fever, pain One of the most widely used medications in the world
Paracetamol

(Acetaminophen)

 Analgesic, antipyretic Fever, pain

PREVIOUS WEEK: MAGNETISM, PROPELLANTS, STEM CELLS
~~~~~
NEXT WEEK: ENVIRONMENTAL CHEMISTRY, VACCINES

19 January 2010 | Tags: , | No Comments »

General Science #9 | Study Material::General Studies | IAS Help

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PHYSICS: MAGNETISM

Overview

  • The term magnetism describes how materials respond to an applied magnetic field
  • All materials are influenced to a greater or lesser extent by the presence of a magnetic field. Some are attracted (paramagnetism) while some are repulsed (diamagnetism)
  • Substances that are negligibly attracted by magnetic fields are called non-magnetic materials. Eg: copper, aluminium, water, glass
  • The magnetic state of a material depends on its temperature, with the result that a substance may exhibit different magnetic characteristics depending on its temperature
  • Magnetism can arise from either intrinsic magnetic moments contained in particles, or by electric currents applied to the substance
  • Magnet is a material that produces a magnetic field
  • Permanent magnet is a material that retain its magnetic field

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Types of magnetism

  • Diamagnetism
    • Diamagnetism is the tendency of a material to oppose a magnetic field
    • It appears in all materials. However, in a material with paramagnetic properties, the paramagnetic behaviour dominates
    • Diamagnetic materials do not have unpaired electrons
    • Superconductors are diamagnetic materials
  • Paramagnetism
    • Paramagnetism is the tendency of a material to be attracted to an applied magnetic field
    • Paramagnetism only occurs in the presence of an externally applied magnetic field. When the external field is removed, the magnetisation will drop to zero
    • Paramagnetic materials have one unpaired electron, allowing it to orient in the direction of the magnetic field
    • Oxygen, myoglobin are examples of paramagnets
  • Ferromagnetism
    • Ferromagnetism is the only type of magnetism that can produce forces strong enough to be felt, and is responsible for the magnetic phenomena in everyday life
    • Ferromagnetic materials have unpaired electron, but unlike paramagnets, they remain oriented even after the external magnetic field has been removed
    • Ferromagnetic materials remain magnetized even after the external applied magnetic field has been removed
    • All permanent magnets are either ferromagnets or ferrimagnets
    • Eg: refrigerator magnets
  • Antiferromagnetism
    • Magnetic moments of electrons point in opposite directions
    • Anitferromagnets have zero net magnetic field
    • They are not very common and usually occur only low temperatures
    • Antiferromagnetism disappears above the Neel Temperature and the material becomes paramagnetic
    • Examples include hematite, chromium, iron manganese
  • Ferrimagnetism
    • Neighbouring pairs of electrons point in opposite direction
    • However, ferromagnetic materials retain their magnetisation in the absence of the magnetic field
    • Example is magnetite

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Electromagnets

  • Electromagnet is a magnet whose magnetic field is produced by the flow of electric current
  • The magnetic field disappears when the current ceases
  • The electromagnet was invented by William Sturgeon (Britain) in 1824
  • Electromagnets are widely used in electrical devices such as motors, generators, loudspeakers, particle accelerators
  • Magnetic Levitation (MAGLEV) trains run on electromagnetic suspension produced by electromagnets

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Earth’s magnetic field

  • The Earth’s magnetic field, which extends several tens of thousands of km into space is called the magnetosphere
  • The earth’s magnetic field is explained by dynamo theory. The theory explains the mechanism by which celestial bodies like the earth, or a star generate magnetic fields. According to the theory, earth’s magnetic field is produced by electric currents in the liquid outer core
  • The magnetic north pole of the Earth is located near the geographic south pole, and the magnetic south pole is located near the geographic north pole. This can be explained by understanding that the north pole of a suspended magnet points towards the north, indicating that the geographic north pole should have south polarity
  • The earth’s magnetic poles move with time due to magnetic changes in the earth’s core. Currently, the magnetic north pole lies near Ellesmore Island in northern Canada, while the south pole is near Wilkes Land, Antarctica. The north pole is moving northwest by about 64 km/year and the south pole is moving northwest by 10-15 km/year

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CHEMISTRY: PROPELLANTS

Overview

  • A propellant is a material that is used to propel an object
  • The object is usually expelled by the pressure created by a gas
  • This pressure may be created by a compressed gas or by a gas produced by a chemical reaction
  • Propellants may be solids, liquids, gases or plasmas
  • Common chemical propellants consist of a fuel and an oxidiser

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Types of propellants

  • Aerosol sprays
    • Aerosol spray is a dispensing system that creates an aerosol (fine) mist of liquid particles
    • In aerosol sprays, the propellant is simply a pressurised gas in equilibrium with its liquid form
    • As some gas escapes to expel the payload, more liquid evaporates thereby maintaining an even pressure
    • The aerosol spray can was invented by Erik Rotheim (Norway) in 1927
    • Aerosol sprays are typically used to dispense insecticides, deodorants and paints
  • Propellants used for propulsion
    • Rockets typically use bipropellants, which contain a combination of a fuel and an oxidiser. Tripropellants, which are not used commonly, use liquid hydrogen as a third component to provide additional efficiency
    • Propellants are usually made from low explosives, which deflagrate (burn) rather than detonate (explode)
    • The controlled burning of the propellants produces thrust by gas pressure which is then used to accelerate a rocket, projectile or other vehicles
    • Propellants are commonly used in rockets, firearms and artillery

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Solid propellants

  • Solid propellants are used for rockets, firearms and artillery
  • Examples of solid propellants include gunpowder (sulphur + charcoal + potassium nitrate), nitrocellulose and cordite
  • Single based propellants: They have nitrocellulose as its chief ingredient. Stabilizers and other chemicals may be added for chemical stability
  • Double based propellants: they contain nitrocellulose with nitroglycerin or other liquid nitrate explosives added. Nitroglycerin reduces smoke and increases energy output. Used in small arms, cannons, mortars and rockets
  • Triple based propellants: consist of nitrocellulose, nitroquanidine, and nitroglycerin or other nitrate explosives. Used in cannons
  • Composite propellants: consist of a fuel such as metallic aluminium, a binder such as synthetic rubber and an oxidiser such as ammonium perchlorate. Used in large rocket motors such as spacecraft
  • Solid propellants have been used since the 11th century to power rockets based on gunpowder
  • Solid fuel rockets offer ease of handling, reliability and long storage periods
  • Solid fuel rockets are used for missiles due to their long storage periods and reliability of launch on short notice
  • Currently, solid fuel rockets are not used for space explorations, but are commonly used as booster rockets to launch spacecraft

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Liquid propellants

  • Liquid propellants are usually used in combinations of fuel and oxidiser
  • Common liquid propellant combinations include
    • Liquid oxygen and liquid hydrogen
    • Liquid oxygen and kerosene
    • Nitrogen tetraoxide and kerosene
  • Liquid fuel rockets are desirable because they offer higher energy output, they can be throttled and shut down and can be reused
  • Liquid fuel rockets are used to power space shuttles
  • A variant of liquid fuel engine is cryogenic fuel engine – these are engines that use gases which are super-cooled into their liquid forms

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Propellants used in the PSLV

  • The Polar Satellite Launch Vehicle (PSLV) has a four stage propulsion system, using solid and liquid propellants alternately
  • First stage: solid – Hydroxyl terminated polybutadiene (HTPB)
  • Second stage: liquid – unsymmetrical di-methyl hydrazine (UDMH) as fuel and nitrogen tetraoxide as oxidiser
  • Third stage: solid – HTPB
  • Fourth stage: solid – mono methyl hydrazine as fuel and mixed oxides of nitrogen as oxidiser

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Propellants used in the GSLV

  • The Geosynchronous Satellite Launch Vehicle (GSLV) is a three stage launch vehicle using solid, liquid and cryogenic propellants
  • First stage – solid – HTPB
  • Second stage – liquid – UDMH as fuel and nitrogen tetraoxide as oxidiser
  • Third stage – cryogenic – liquid hydrogen and liquid oxygen

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BIOLOGY: STEM CELLS

Overview

  • Stem cells are cells that can renew themselves.
  • Stem cells renew themselves through mitotic cell division and can differentiate into a diverse range of specialised cell types
  • Stem cells are found in most multi-cellular organisms
  • There are two types of stem cells in mammals
    • Embryonic stem cells
    • Adult stem cells
  • Stem cells are mainly found in blood from the umbilical cord and the bone marrow
  • Due to their self-renewing nature, stem cells are very important for treatment of diseases

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Importance of stem cells

  • For a cell to be characterised as a stem cell, it must exhibit the following properties
    • Self renewal: the ability to go through numerous cycles of cell division while maintaining the undifferentiated state
    • Potency: the capacity to differentiate into specialised cell types
  • In developing embryos, stem cells can differentiate into all of the specialised embryonic tissues
  • In adult organisms, stem cells act as a repair system for the body, replenishing specialised cells
  • Stem cells also maintain the normal turnover of regenerative organs such as blood, skin or tissues
  • Stem cells can be grown and transformed into specialised cells of various tissues such as muscles and nerves using cell culture
  • Stem cell treatment holds the potential of transforming human medicine, wherein stem cells introduce new cells into damaged tissue in order to treat a disease or injury
  • The ability of stem cells to self renew and differentiate offers the potential to replace diseased and damaged tissue without the risk of rejection or side effects

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Current stem cell treatments

  • Currently, stem cell treatment is available to treat the side effects of chemotherapy on cancer patients, such as leukaemia or lymphoma
  • During chemotherapy most growing cells are killed by cytotoxic agents
  • These agents kill not only the leukaemia cells but also healthy haematopoietic stem cells in adjacent bone marrows.
  • Using stem cell therapy, healthy bone marrow stem cells are used to reintroduce healthy stem cells to replace those lost in the treatment

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Potential stem cell treatments

  • Stem cells can be potentially used to treat a number of serious diseases. These include
    • Brain diseases such as Parkinson’s and Alzheimer’s
    • Cancers
    • Spinal cord injury
    • Heart damage
    • Haematopoiesis (blood cell formation)
    • Baldness, missing teeth
    • Blindness, deafness
    • Diabetes
    • Neural damage
  • Almost all these treatments are still in the research stage
  • In Jan 2009, the US Food and Drug Administration (FDA) gave clearance to Geron Corporation for the first clinical trials of an embryonic stem cell therapy on humans. The trial will evaluate the efficacy of the drug GRNOPC1 on patients with spinal cord injury

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Important milestones in stem cell research

  • 1963: Ernest McCullogh (Canada) and James Till (Canada) illustrate the presence of self renewing cells in the bone marrow
  • 1968: Bone marrow transplant between two siblings successfully treats Severe Combined Immunodeficiency (SCID)
  • 1978: haematopoietic stem cells discovered in human blood
  • 1998: James Thomson (USA) derives the first human embryonic stem cell line
  • 2001: Scientists at Advanced Cell Technology (USA) clone first early human embryos for the purpose of generating embryonic stem cells
  • 2006: Scientists at Newcastle University (England) create first every artificial liver cells using umbilical cord blood cells
  • 2008: Robert Lanza and colleagues at ACT create first human embryonic stem cells without destruction of the embryo

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PREVIOUS WEEK: ELECTRICITY, EXPLOSIVES, CLONING
~~~~~
NEXT WEEK: MEDICAL IMAGING, MEDICINAL CHEMISTRY

12 January 2010 | Tags: , , | 2 Comments »

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PHYSICS: ELECTRICITY

Overview

  • Electricity is an extraordinarily versatile source of energy
  • Electricity is the backbone of modern industrial society
  • The phenomenon of electricity includes concepts such as
    • Electric charge: a property of subatomic particles that determines their electromagnetic interactions
    • Electric current: a movement or flow of charged particles
    • Electric field: influence of charged particles on other charged particles in the vicinity
    • Electric potential: capacity of an electric field to do work
    • Electromagnetism: interaction between electric and magnetic fields

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TIMELINE OF EARLY DISCOVERIES/INVENTIONS


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BASIC ELECTRICAL COMPONENTS
  1. Resistors
    1. Resistors are materials that resist the flow of current through them
    2. They dissipate energy in the form of heat
    3. Ohmic materials are those materials whose resistance remains constant over a range of temperatures and currents. Non-ohmic materials have resistances that change
    4. The unit of resistance is Ohm
  2. Capacitors
    1. Capacitors are devices that store electric energy in the form of electric charge
    2. They usually consist of two conducting plates separated by a thin insulating layer
    3. Capacitors block steady state current i.e. DC current
    4. The unit of capacitance is Farad
  3. Inductors
    1. Inductors are conductors that store energy in a magnetic field, which is produced in response to an electrical current
    2. Inductors allow steady current, but oppose rapidly changing currents
    3. The unit of inductance is Henry
  4. Transformers
    1. A transformer is a device that transfers electrical energy from one circuit into another
    2. This transfer occurs through inductively coupled conductors, where varying current in one circuit creates a varying magnetic field (and hence voltage) in the other circuit
    3. Transformers can be used to step-up or step-down voltages from high voltage transmission lines to appliances in homes

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ELECTRICITY IN NATURE
  1. Electric shock
    1. A voltage applied to the human body causes an electric current through the tissues
    2. In general, greater the voltage applied, greater the current passed through the tissues
    3. Voltages 100-250 V can be lethal in humans, although as low 32V has been lethal sometimes. Lethality increases dramatically beyond 250V
    4. If the current is sufficiently high, it can cause muscle contractions, fibrillation of the heart and tissue burns
    5. DC tends to cause continuous muscle contractions making the victim hold on to a live conductor, thereby increasing risk of tissue burn
    6. AC tends to interfere with heart function, increasing risk of cardiac arrest
    7. AC at high frequencies, causes current to travel on the surface due to skin effect. This results in severe burn but is usually not fatal
  2. Electrical phenomena
    1. Touch, friction and chemical bonding are all due to interactions between electrical fields on the atomic scale
    2. The Earth’s magnetic arises from a natural dynamo of circulating currents in the planet’s core
    3. Piezoelectric crystals like quartz and sugar generate electric current when subject to mechanical pressure
    4. Electric eels detect and stun their prey via high voltages (500 V) generated from muscle cells called electrocytes
    5. Electrical currents, called Action Potential, are used for nervous system communication in all animals, including humans

CHEMISTRY: EXPLOSIVES

Overview

  • An explosive is a substance that contains a great deal of stored energy that can produce an explosion, usually accompanied by the production of light, heat and pressure
  • The energy stored in an explosive material may be
    • Chemical energy such as nitroglycerine
    • Pressurised compressed gas such as a gas cylinder or aerosol can
    • Nuclear energy such as Uranium and plutonium

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CHEMICAL REACTIONS IN EXPLOSIVES
  1. Deflagration
    1. Deflagration is a term that describes subsonic combustion that propagates through thermal conductivity
    2. Deflagration is easier to control and so is used when the goal is to move an object with the force of expanding gas
    3. Examples of deflagration include gas stove, internal combustion engine, gunpowder, pyrotechnics etc
  2. Detonation
    1. Detonation is a combustion process in which a supersonic shock wave through the body of a material
    2. In detonation, a supersonic shock wave originating at the point of ignition compresses the surrounding material, thus increasing its temperature to the point of ignition
    3. Because detonations generate high pressures, they are much more destructive than deflagrations
    4. Detonations are difficult to control and are used primarily for demolition and in warfare.
    5. Examples of detonation includes high explosives, oxygen-methane mixture

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CLASSIFICATION OF EXPLOSIVES
  1. High explosives
  • Materials that explode faster than the speed of sound are called high explosives
  • This type of explosion is known as detonation
  • Used in mining, demolition and military applications
  1. Low explosives
    1. Materials that explode slower than the speed of sound are called low explosives.
    2. This type of explosion is known as deflagration
    3. Used as propellants, gun powder, pyrotechnics (such as flares and fireworks)
  2. Primary explosives
    1. A primary explosive is an explosive that is extremely sensitive to stimuli. These stimuli include impact, friction, heat, static electricity and electromagnetic radiation
    2. For primary explosives, a relatively small amount of energy is required for initiation of explosion
    3. In general, primary explosives are considered to be those explosives that are more sensitive than PETN
    4. Used in detonators to trigger larger charges of more stable secondary explosives
    5. E.g.: Mercury fulminate, Nitrogen trichloride, acetone peroxide, ammonium permanganate
  3. Secondary explosives
    1. Secondary explosives are less sensitive than primary explosives and require more energy to be initiated
    2. They are safer to handle and store
    3. In general, secondary explosives are considered to be those explosives that are less sensitive than PETN
    4. Secondary explosives are usually used in large quantities and are initiated by small amounts of primary explosives
    5. E.g.: TNT, RDX

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SOME COMMON EXPLOSIVES
  1. Trinitrotoluene (TNT)
    1. TNT is a useful explosive material with convenient handling properties. TNT is sometimes also used as a reagent in chemical synthesis
    2. TNT was first prepared by Joseph Wilbrand (GermanY) in 1863
    3. The explosive yield of TNT is considered to be the standard measure of strength of bombs and other explosives
    4. Sulphitation is a process used in the manufacture of TNT, specifically to stabilize the explosive
    5. TNT is one of the most commonly used explosives for industrial and military applications
    6. It is insensitive to shock and friction, reducing the occurrence of accidental detonation. TNT melts without exploding (allowing it to be combined with other explosives), does not absorb or dissolve in water (allowing use in wet environments) and is stable compared to other explosive
    7. TNT contains energy of 4.6 Mega Joules per kilogram (MJ/kg). By comparison gun powder contains 3 MJ/kg, dynamite contains 7.5 MJ/kg and gasoline contains 47.2 MJ/kg
    8. TNT is used as a reference for other explosives. Nuclear weapons have energy content measured in kilotonnes (kT) or megatonnes (MT) of TNT equivalent.
    9. TNT is usually used in mixture with other substances. E.g.: Amatol (TNT + ammonium nitrate)
  2. RDX
    1. RDX, chemically cyclotrimethylnetrinitramine, is also known as cyclonite and T4
    2. RDX is usually used in mixture with other explosives and plasticizers
    3. RDX is stable in storage and is considered one of the most powerful of military explosives
    4. RDX was discovered in 1898 by Goerg Friedrich Henning (Germany)
  3. Pentaerythritol tetranitrate (PETN)
    1. PETN is one of the most powerful high explosives known
    2. It is more difficult to detonate than primary explosives, but less stable than secondary explosives
    3. It is more sensitive than other high explosives, and is rarely used alone
    4. Usually used in small calibre ammunition, detonators of land mines
    5. PETN is an effective underwater explosive
    6. PETN is a major ingredient of Semtex (plastic explosive)
    7. PETN was first synthesised by Bernhard Tollens (Germany) in 1891
  4. Dynamite
    1. Dynamite is based on nitroglycerine
    2. It was invented by Alfred Nobel (Sweden) in 1867
    3. Used mainly for mining, quarrying, construction
    4. Dynamite was the first safely manageable explosive stronger than black powder
  5. Plastic explosive
    1. Plastic explosives are explosives that are soft and can be moulded by hand
    2. Common plastic explosives include Semtex (Czech Republic) and C-4 (USA)
    3. Used mainly for demolition, also used by terrorists
    4. The first plastic explosive was Gelignite, invented by Alfred Nobel (Sweden) in 1875
    5. C-4 (composition 4) is made of RDX while Semtex is made from RDX and PETN
    6. Semtex became notoriously popular with terrorists because it is difficult to detect. Semtex was invented by Stanislav Berbera (Czech R.) in the 1950s

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BIOLOGY: CLONING

Overview

  • Cloning is the process by which genetically identical individuals are produced
  • Cloning happens in nature by the biological mechanisms of asexual reproduction in bacteria, insects and plants
  • Cloning can also be performed artificially by copying fragments of DNA (molecular cloning) or cells (cell cloning) or organisms
  • Mammals, which reproduce sexually, cannot clone naturally. Mammals inherit genetic material half each from both parents, meaning that the progeny is never an identical replica of the parent. Natural clones in mammals are confined to the production of identical twins
  • The first vertebrate to be cloned was a tadpole by Robert Briggs (USA) and Thomas King (USA) in 1952

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Cloning in plants

  • Plants have been clone for a long time.
  • Grafting is a form of plant cloning
  • Many horticulture plants are cloned, having been derived from a single individual
  • Examples of plant cloning include carrots, tobacco, potato, banana

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Cloning in animals

  • Cloning of animals is based on a technique known as “somatic cell nuclear transfer”.
  • Nuclear transfer involves fusing two cells together – a donor cell containing all its DNA, and egg cell with all its DNA removed
  • The two cells are fused with an electric pulse and the resulting enucleated egg is implanted in the mother

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Dolly the Sheep

  • Dolly, a Finn Dorset ewe, was the first mammal to be successfully cloned from an adult cell
  • Dolly was cloned by Ian Wilmut and Keith Campbell at the Roslin Institute in Edinburgh (Scotland)
  • Dolly was born in 1996 and lived for six years
  • The donor cell for Dolly was taken from a mammary gland.
  • Production of a healthy clone proved that a cell from a specific part of the body could recreate a whole individual

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Some animals that have been cloned

See here for the full list cloned animals.

Cloned animal When Where By whom Notes
Tadpole 1952 USA Robert Briggs, Thomas King
Carp (fish) 1963 China Tong Dizhou
Mice

(first cloned mammal)

 1986 Soviet Union Chaylakhyan, Veprencev, Sviridova, Nikitin First cloned mammal
Sheep

(first cloned mammal from adult cell)

 1996 Britain Ian WIlmut, Keith Campbell First cloned mammal from adult cell
Rhesus monkey

(named Tetra)

 2000 It was named Tetra
Gaur (Asian Ox) 2001 USA Jonathan Hill, Philip Damiani Named Noah

First endangered species to be cloned
Cat 2001 (Copycat)

2004 (Little Nicky)

 USA Copycat was the first cloned pet

Little Nicky was the commercially produced cat clone
Mule (named Idaho Gem) 2003 USA Gordon Woods, Dirk Vanderwall First clone in horse family
Horse (named Prometea) 2003 Italy Cesare Galli First cloned horse

First animal to be born from and carried by its cloning mother
Water buffalo

(called Samrupa)

 2009 India
 S K Singla and others at Karnal National Dairy Research Institute First cloned buffalo

Died 5 days after birth due to lung infection
Camel

(called Injaz)

 2009 Dubai Nisar Ahmad Wani First cloned camel

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PREVIOUS WEEK: PARTICLE PHYSICS, CERAMICS, GENETIC ENGINEERING
~~~~~
NEXT WEEK: PROPELLANTS, STEM CELLS

5 January 2010 | Tags: , , | No Comments »

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PHYSICS: PARTICLE PHYSICS

Overview

  • The atom was discovered by John Dalton in 1802
  • However, even more fundamental particles were discovered in the 20th century
  • Particle physics focuses on subatomic particles including electrons, protons and neutrons
  • Many fundamental particles do not occur in nature but can be created in high energy collisions of other particles

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Standard Model of particle physics

  • The Standard Model describes the current classification of elementary particles
  • It describes strong, weak and electromagnetic forces using gauge bosons
  • The Standard Model does not include gravitation, dark matter and dark energy
  • The Standard Model was developed by Sheldon Glashow, Steven Weinberg and Abdus Salam in the 1960s. They won Nobel in Physics in 1979
  • The Model contains 24 fundamental particles
  • It predicts the existence of the Higgs Boson, which is yet to discovered
  • All particles of the Standard Model have been observed in experiments, except the Higgs Boson

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Elementary particles

  • All elementary particles are either fermions or bosons
  • Fermions are particles associated with matter, while bosons are particles associated with force
  • Fermions can be divided into Quarks and Leptons
  • Bosons can be divided into Gauge Bosons and Other Bosons (including Higgs Boson)
  • Protons and neutrons are examples of Hadrons, which are composites of Quarks
  • Electrons are elementary particles by themselves

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Important particle physics labs

Facility Location Established Famous for
Brookhaven National Lab New York 1947 World’s first heavy ion collider

World’s only polarized proton collider
Budker Institute of Nuclear Physics Novosibirsk (Russia) 1959 World’s first particle accelerator
European Organization for Nuclear Research Geneva 1954 World’s largest particle physics lab

Birthplace of World Wide Web

Large Hadron Collider (LHC)
German Electron Synchrotron (DESY) Hamburg 1959
Fermilab Chicago 1967 Tevatron – world’s second largest particle accelerator
High Energy Accelerator Research Organization (KEK) Tsukuba (Japan)
SLAC National Accelerator Lab Stanford University 1962 Longest linear accelerator in the world

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CHEMISTY: CERAMICS

Overview

  • A ceramic is an inorganic, non-metallic solid prepared by the action of heating and subsequent cooling
  • The earliest ceramic materials were pottery made from clay
  • Ceramics are resistant to chemical erosion and high temperatures (up to 1600C)

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PROPERTIES OF CERAMICS

  • Mechanical properties
    • Ceramic materials are usually formed by ionic or covalent bonds
    • These materials tend to not be elastic and fracture easily
    • Ceramics are also porous
    • In general ceramics have poor toughness and have low tensile strength
  • Electrical properties
    • Some ceramics are semiconductors
    • Semiconducting ceramics are made using zinc oxide
    • Under extremely low temperatures, some ceramics exhibit superconductivity
    • Most ceramics exhibit piezoelectricity i.e. the conversion of mechanical stress to electrical signals. This effect is commonly used in quartz watches
  • Optical properties
    • Ceramics (esp. those based on aluminium oxide) can be made translucent
    • This has immediate applications in sodium-vapour lamps and dental restorations
    • Ceramics can be made transparent with applications in laser technology

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TYPES OF CERAMICS

  1. Structural ceramics such as bricks, pipes, floor, roof tiles etc
  2. Refractory ceramics such as kiln lining, steel and glass making crucibles
  3. Whitewares such as tableware, wall tiles, pottery, sanitary products
  4. Technical ceramics such as jet engine turbine blades, ballistic protection etc

MANUFACTURE OF CERAMICS

  1. Milling
    1. Process by which materials are reduced in size
    2. Involves breaking of cemented material or pulverization
    3. Techniques used include ball mill, roll crusher, jaw crusher, wet attrition mills
  2. Batching
    1. Is the process of weighing the oxides according to recipes and preparing them for further processing
  3. Mixing
    1. Involves mixing the various components in the appropriate proportions
    2. Uses ribbon mixers, Mueller mixers and pug mills
  4. Forming
    1. This is the process of the making the mixed materials into desired shapes such as toilet bowls, spark plugs etc
    2. Forming techniques include extrusion, pressing and slip casting
  5. Drying
    1. Controlled heat is applied to dry the materials and obtain rigid shape
  6. Firing
    1. Dried parts are processed through a controlled heating process and oxides are chemically changed to cause sintering and bonding

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BIO-CERAMICS

  • Bacteria, plants and animals exhibit a tendency to form crystalline materials composed of silicon
  • These bioceramics show exceptional physical properties such as strength, fracture resistance etc
  • Bio-ceramics are usually made of proteins such as keratin, elastin, chitin and collagen
  • The mother-of-pearl portion of marine shells exhibit the strongest mechanical strength and fracture toughness of any non-metallic substance known

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APPLICATIONS OF CERAMICS

Application Ceramic components Notes
Armoured vests Alumina, boron carbide Protects against high-calibre rifle fire
Dental implants, synthetic bone Artificial hydroxyapatite (natural mineral of bone)
Ball bearings Silicon nitride Harder, more resistant to heat than metal bearings
Earthenware Kaolin, boll, flint Opaque

Used to make cups, saucers etc
Chinaware Leached granite (to remove quartz and mica) Translucent

Resists scratching
Porcelain Kaolin, feldspar, quartz White, semi-opaque

Highly resistant to scratching

Stronger than glass
Stoneware Kaolin, feldspar, quartz Similar to porcelain but from poor grade raw materials

Hard, infusible
Space shuttles Extremely pure Silica Used on the outer surface of shuttles to withstand heating during atmospheric re-entry

Space shuttle Colombia burnt up on re-entry due to damage to ceramic tiles

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BIOLOGY: GENETIC ENGINEERING

Overview

  • Genetic engineering refers to the direct manipulation of an organism’s genes
  • Genetic engineering is also referred to as recombinant DNA technology, genetic modification and gene splicing
  • Genetic engineering uses cloning and transformation of molecules to alter the structure and characteristics of genes
  • Examples of genetic engineering include improved crop technologies, synthetic hormones, and creation of experimental mice

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Process of genetic engineering

The process of genetic engineering has five main steps:

  1. Isolation of the genes of interest
  2. Insertion of the genes into a transfer vector
  3. Transfer of the vector to the organism to be modified
  4. Transformation of the cells of the organism
  5. Selection of the genetically modified organisms from those that have not been successfully modified

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Applications of genetic engineering

  • The first genetically engineered medicine was synthetic insulin
  • Genetic engineering has been used to produce vaccines for hepatitis B
  • Creation of genetically modified foods such as soybean, corn, canola and cotton seed oil. GM foods have higher resistance to pests, bacterial/fungal infections, higher yield and higher nutritional value
  • Gene therapy using viruses to treat severe combined immunodeficiency (SCID)
  • Using genetically modified virus to construct environment friendly lithium-ion battery
  • Using human eggs from a second mother to allow infertile women with genetic defects in their mitochondria to have children
  • Artificial DNA, called Synthetic Organism (SO-1), with unknown functions has been created

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Milestones in genetic engineering

  • 1953: James Watson (USA) and Francis Crick (Britain) discover structure of DNA. They win Nobel in Physiology or Medicine in 1979
  • 1973: Stanley Cohen (USA) and Herbert Boyer (USA) develop a technique to clone segments of DNA molecules
  • 1976: Genentech, the first company dedicated to producing genetically engineered products is established in San Francisco. It was founded by Herbert Boyer and Robert Swanson
  • 1979: Genetic engineering used to synthesize insulin
  • 1981: scientists at Ohio university transfer genes from other organisms into mice
  • 1990: Human Genome Project launched
  • 1990: first gene therapy experiment performed on a four-year old girl with adenosine deaminase deficiency. Developed by French Anderson
  • 1996: a yeast known as Saccharomyces cerevisiae is the first eukaryotic genome to be sequenced by more than 100 labs collaboratively around the world
  • 2003: Human Genome Project announces complete mapping of human genome

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GENETICALLY MODIFIED FOODS

  1. BT-Cotton
    1. BT-Cotton is a genetically modified variety of cotton into which Cryiae gene from the bacillus thuriegenois bacteria have been introduced
    2. This gene produces a toxin called BT-Toxin in every part of the plant thereby destroying the dreaded cotton pest Bollworm
    3. This technology was developed by US seed company Monsanto
    4. However, concerns include evolution of super-pests with higher levels of resistance, destruction of agriculturally beneficial organisms like bees, soil microflora etc
  2. Terminator gene
    1. Terminator gene is a seed variety developed using genetic engineering
    2. It causes the seed to self-destruct after it has been used to raise the first generation of crops
    3. This is done in order to prevent farmers from raising subsequent generations of crops without paying royalties
    4. Concerns include this self-destruct gene may be transferred to other plants by cross-pollination leading to extinction of traditional agricultural production
    5. It is also known as Genetic Use Restriction Technology (GURT) and was developed by the US Department of Agriculture in conjunction with the Delta and Pine Land Co.
  3. Golden rice
    1. Type of rice crop provided with a gene to develop Beta-Carotene
    2. This helps production of vitamin A in the body
    3. This helps fight vitamin A deficiency, the primary cause of childhood blindness
    4. Beta-carotene gives rice a yellow colour and hence is called Golden Rice
    5. Created by Swiss Federal Institute of Technology
  4. GM Cabbage
    1. Cabbage that will resistant to attack of Diamond Back Moth
    2. Developed by Indian Agricultural Research Institute (New Delhi)

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PHYSICS: NUCLEAR PHYSICS

Nuclear Fission

  • Nuclear fission is a reaction in which the nucleus of an atom splits into smaller parts
  • Nuclear fission can either release energy or absorb energy: for nuclei lighter than iron fission absorbs energy, while for nuclei heavier than iron it releases energy
  • Energy released can be in the form of electromagnetic radiation or kinetic energy
  • The amount of free energy contained in nuclear fuel is about a million times that contained in a similar mass of chemical fuel (like petrol)
  • The atom bomb or fission bomb is based on nuclear fission
  • Example: fission of Uranium-235 to give Barium, Krypton and neutrons

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Nuclear Fusion

  • Nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus
  • Nuclear fusion can result in either the release or absorption of energy: for nuclei lighter than iron fusion releases energy, while for nuclei heavier than iron it absorbs energy
  • Nuclear fusion is the source of energy of stars.
  • Nuclear fusion is responsible for the production of all but the lightest elements in the universe. This process is called nucleosynthesis
  • Controlled nuclear fusion can result in a thermonuclear explosion – the concept behind the hydrogen bomb
  • The energy density of nuclear fusion is much greater than that of nuclear fission
  • Only direct conversion of mass into energy (collision of matter and anti matter) is more energetic than nuclear fusion
  • Example: fusion of hydrogen nuclei to form helium

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PIONEERS OF NUCLEAR PHYSICS RESEARCH
Scientist

Nationality

Discovery

Recognition
J J Thomson

Britain

Electron (1897)

Nobel in Physics (1906)
Henri Becquerel

Belgium

Radioactivity (1896)

Nobel in Physics (1903)
Ernest Rutherford

New Zealand

Structure of atom (1907)

Nobel in Chemistry (1908)

He is regarded as the father of nuclear physics
Franco Rasetti

Italy/USA

Nuclear spin (1929)
James Chadwick

Britain

Neutron (1932)

Nobel in Physics (1935)
Enrico Fermi

Italy/USA

Nuclear chain reaction (1942)

Neutron irradiation

Nobel in Physics (1938)
Hideki Yukawa

Japan

Strong nuclear force (1935)

Nobel in Physics (1949)
Hans Bethe

Germany/USA

Nuclear fusion (1939)

Nobel in Physics (1967)

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APPLICATIONS OF NUCLEAR PHYSICS

Application

Developed by

Working principle

Use

Nuclear power

Enrico Fermi (Italy, 1934)

Nuclear fission

Power generation

Nuclear weapons

Enrico Fermi (Italy, 1934)

Edward Teller (USA, 1952)

Nuclear fission

Nuclear fusion

Weapons

Radioactive pharmaceuticals

Sam Seidlin (USA, 1946)

Radioactive decay

Cancer, endocrine tumours, bone treatment

Medical imaging

David Kuhl, Roy Edwards (USA, 1950s)

Nuclear magnetic resonance (for MRI)

Positron emission (for PET)

MRI: Musculosketal, cardiovascular, brain, cancer imaging

PET: cancer, brain diseases imaging

Radiocarbon dating

Willard Libby (USA, 1949)

Radioactive decay of carbon-14

Archaeology

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IMPORTANT NUCLEAR RESEARCH FACILITIES

Nuclear research facilities in the world

Facility

Location

Established

Famous for
Brookhaven National Lab

New York

1947

Until 2008 world’s largest heavy-ion collider
European Organization for Nuclear Research (CERN)

Geneva

1954

World’s largest particle physics lab

Birthplace of the World Wide Web

Large Hadron Collider (LHC)
Fermilab

Chicago

1967

Tevatron – world’s second largest particle accelerator
ISIS

Oxfordshire (England)

1985

Neutron research
Joint Institute for Nuclear Research

Dubna, Russia

1956

Collaboration of 18 nations including former Soviet states, China, Cuba
Lawrence Berkeley National Lab

California

1931

Discovery of multiple elements including astatine, and plutonium
Lawrence Livermore National Lab

California

1952
Los Alamos National Lab

New Mexico, USA

1943

The Manhattan Project
National Superconducting Cyclotron lab

Michigan

1963

Rare isotope research
Oak Ridge National Lab

Tennessee

1943

World’s fastest supercomputer – Jaguar
Sudbury Neutrino Lab

Ontario

1999

Located 2 km underground

Studies solar neutrinos
TRIUMF (Tri University Meson Facility)

Vancouver

1974

World’s largest cyclotron
Yongbyon Nuclear Scientific Research Centre

Yongbyon, North Korea

1980

North Korea’s main nuclear facility
Sandia National Lab

New Mexico, USA

1948

Z Machine (largest X-ray generator in the world)
Institute of Nuclear Medicine, Oncology and Radiotherapy (INOR)

Abbottabad, NWFP (Pakistan)
Pakistan Institute of Nuclear Science and Technology (PINSTECH)

Islamabad

1965

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Nuclear research facilities in India

Facility

Location

Established

Famous for

Bhabha Atomic Research Centre

Bombay

1954

India’s primary nuclear research centre

India’s first reactor Apsara

Variable Energy Cyclotron Centre (VECC)

Calcutta

1977

First cyclotron in India

Institute for Plasma Research (IPR)

Gandhinagar

1982

Plasma physics

Indira Gandhi Centre for Atomic Research (IGCAR)

Kalpakkam

1971

Fast breeder test reactor (FBTR)

KAMINI (Kalapakkam Mini) light water reactor

Built the reactor for Advanced Technology Vessel (ATV)

Saha Institute for Nuclear Physics

Calcutta

1949

Tata Institute for Fundamental Research (TIFR)

Bombay

1945

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CHEMISTRY: POLYMERS

Overview

  • A polymer is a large molecule consisting of repeating structural units
  • The repeating units are usually connected by covalent chemical bonds
  • Polymers can be of two types
    • Natural polymers: shellac, amber, rubber, proteins etc
    • Synthetic polymers: nylon, polyethylene, neoprene, synthetic rubber etc
  • Synthetic polymers are commonly referred to as plastics
  • The first plastic based on a synthetic polymer to be created was Bakelite, by Leo Baekeland(Belgium/USA) in 1906
  • Vulcanization of rubber was invented by Charles Goodyear (USA) in 1839. Vulcanization is the process of making rubber more durable by addition of sulphur
  • The first plastic to be created was Parkesine (aka celluloid) invented by Alexander Parkes (England) in 1855

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Synthesis of polymers

  • The synthesis of polymers – both natural and synthetic – involves the step called polymerization
  • Polymerization is the process of combining many small molecules (monomers) into a covalently bonded chain (polymer)
  • Synthetic polymers are created using of two techniques
    • Step growth polymerization: chains of monomers are combined directly
    • Chain growth polymerization: monomers are added to the chain one at a time
  • Natural polymers are usually created by enzyme-mediated processes, such as the synthesis of proteins from amino acids using DNA and RNA

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Categories of polymers

  • Organic polymers are polymers that are based on the element carbon. Eg: polyethylene, cellulose etc
  • Inorganic polymers are polymers that are not based on carbon. Eg: silicone, which uses silicon and oxygen
  • Copolymer is one that is derived from two or more monomeric units. Eg: ABS plastic
  • Fluoropolymers are polymers based on fluorocarbons. They have high resistance to solvents, acids and bases. Eg: teflon

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TYPES OF BIOPOLYMERS

DNA as a biopolymer

DNA as a biopolymer

  1. Structural proteins
    1. Structural proteins are proteins that provide structural support to tissues
    2. They are usually used to construct connective tissues, tendons, bone matrix, muscle fibre
    3. Examples include collagen, keratin, elastin
  2. Functional proteins
    1. Proteins that perform a chemical function in organisms
    2. Usually used for initiate or sustain chemical reactions
    3. Examples include hormones, enzymes
  3. Structural polysaccharides
    1. They are carbohydrates that provide structural support to cells and tissues
    2. Examples include cellulose, chitin
  4. Storage polysaccharides
    1. Carbohydrates that are used for storing energy
    2. Eg: starch, glycogen
  5. Nucleic acids
    1. Nucleic acids are macromolecules composed of chains of nucleotides
    2. Nucleic acids are universal in living beings, as they are found in all plant and animal cells
    3. Eg: DNA, RNA

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TYPES OF SYNTHETIC POLYMERS
  1. Thermoplastics
    1. Thermoplastics are plastics that turn into liquids upon heating
    2. Also known as thermosoftening plastic
    3. Thermoplastics can be remelted and remoulded
    4. Eg: polyethylene, Teflon, nylon
    5. Recyclable bottles (such as Coke/Pepsi) are made from thermoplastics
  2. Thermosetting plastics
    1. Thermosettings plastics are plastics that do not turn into liquid upon heating
    2. Thermosetting plastics, once cured, cannot be remoulded
    3. They are stronger, more suitable for high-temperature applications, but cannot be easily recycled
    4. Eg: vulcanized rubber, bakelite, Kevlar
  3. Elastomers
    1. Elastomers are polymers that are elastic
    2. Elastomers are relatively soft and deformable
    3. Eg: natural rubber, synthetic polyisoprene

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IMPORTANT NATURAL POLYMERS AND THEIR APPLICATIONS
Polymer

Application

Notes
Collagen

Connective tissue

Gelatine (food)

Most abundant protein in mammals
Keratin

Hair, nails, claw etc
Enzymes

Catalysis
Hormones

Cell signalling
Cellulose

Cell wall of plants

Cardboard, paper

Most common organic compound on Earth
Chitin

Cell wall of fungi, insects
Starch

Energy storage in plants

Most important carbohydrate in human diet
Glycogen

Energy storage in animals
DNA

Genetic information
RNA

Protein synthesis

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IMPORTANT SYNTHETIC POLYMERS AND THEIR APPLICATIONS
Polymer

Developed by

Constituent elements

Application

Notes
Parkesine

Alexander Parkes (Britain, 1855)

Cellulose

Plastic moulding

First man-made polymer
Bakelite

Leo Baekeland (USA, 1906)

Phenol and formaldehyde

Radios, telephones, clocks

First polymer made completely synthetically
Polyvinylchloride (PVC)

Henri Regnault (France, 1835)

Vinyl groups and chlorine

Construction material

Third most widely used plastic
Styrofoam

Ray McIntre (USA, 1941)

Phenyl group

Thermal insulation

Brand name for polystyrene
Nylon

Wallace Carothers (USA, 1935)

Amides

Fabric, toothbrush, rope etc

Family of polyamides

First commercially successful synthetic polymer
Synthetic rubber

Fritz Hoffman (Germany, 1909)

Isoprene

Tyres, textile printing, rocket fuel
Vulcanized rubber

Charles Goodyear (USA, 1839)

Rubber, sulphur

Tyres

Vulcanized rubber is much stronger than natural rubber
Polypropylene

Karl Rehn and Guilio Natta (Italy, 1954)

Propene

Textiles, stationary, automotive components

Second most widely used synthetic polymer
Polyethylene

Hans von Pechmann (Germany, 1898)

Ethylene

Packaging (shopping bags)

Most widely used synthetic polymer
Teflon

Roy Plunkett (USA, 1938)

Ethylene

Cookware, construction, lubricant

Brand name for polytetrafluoroehtylene (PTFE)

Very low friction, non-reactive

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DEGRADATION OF POLYMERS

Ozone cracking in natural rubber tubing

Ozone cracking in natural rubber tubing

  • Degradation of polymers can be desirable as well undesirable: desirable when looking for biological degradation, undesirable when faced with loss of strength, colour etc
  • Polymer degradation usually occurs due to hydrolysis of covalent bonds connecting the polymer chain
  • Polymer degradation can happen because of heat, light, chemicals and galvanic action
  • Ozone cracking is the cracking effect of ozone on rubber products such as tyres, seals, fuel lines etc. Usually prevented by adding antiozonants to the rubber before vulcanization
  • Chlorine can cause degradation of plastic as well, especially plumbing
  • Resin Identification Code is the system of labelling plastic bottles on the basis of their constituent polymers. This Code helps in the sorting and recycling of plastic bottles
  • Degradation of plastics can take hundreds to thousands of years

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Biodegradable plastics

  • Biodegradable plastics are plastics than can break down upon exposure to sunlight (especially UV), water, bacteria etc
  • Biopol is a biodegradable polymer synthesized by genetically engineered bacteria
  • Ecoflex is a fully biodegradable synthetic polymer for food packaging

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Bioplastics

  • They are organic plastics derived from renewable biomass sources such as vegetable oil, corn, starch etc

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Oxy-biodegradable plastics

  • Plastics to which a small amount of metals salts have been added
  • As long as the plastic has access to oxygen the metal salts speed up process of degradation
  • Degradation process is shortened from hundreds of years to months

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BIOLOGY: GENETIC DISORDERS

About genetic disorders

Huntington's disease is inherited in the autosomal dominant fashion

Huntington's disease is inherited in the autosomal dominant fashion

  • Genetic disorders are disorders that are passed on from generation to generation
  • They are caused by abnormalities in genes or chromosomes
  • Some genetic disorders may also be influenced by non-genetic environmental factors. Eg: cancer
  • Most genetic disorders are relatively rare and only affect one person in thousands or millions
  • To recollect, males have XY chromosome pairs while females have XX pairs

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Single Gene Disorders

  • Single gene disorders result from the mutation of a single gene
  • They can be passed onto subsequent generations in multiple ways
  • Single gene disorders include sickle cell disease, cystic fibrosis Huntington disease

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Multiple gene disorders

  • Multiple gene disorders result from mutation on multiple genes in combination with environmental factors
  • They do not have a clear pattern of inheritance, which makes it difficult to assess risk of inheriting a particular disease
  • Examples include heart disease, diabetes, hypertension, obesity, autism

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TYPES OF SINGLE GENE GENETIC DISORDERS
  1. Autosomal dominant

    Sickle cell disease is inherited in the autosomal recessive pattern

    Sickle cell disease is inherited in the autosomal recessive pattern

    1. Only one mutated copy of the gene is necessary for inheritance of the mutation
    2. Each affected person usually has one affected parent
    3. There is a 50% chance that the child will inherit the mutated gene
    4. Autosomal dominant disorders usually have low penetrance i.e. although only one mutated copy is needed, only a small portion of those who inherit that mutation will develop the disorder
    5. Eg: Huntington’s disease, Marfan syndrome
  2. Autosomal recessive
    1. Two copies of the gene must be mutated for a person to be affected
    2. An affected person usually has unaffected parents who each have one mutated gene
    3. There is a 25% chance that the child will inherit the mutated gene
    4. Eg: Cystic fibrosis, sickle cell disease, Tay-Sachs disease, dry earwax, Niemann-Pick disease
  3. X-linked dominant
    1. X-linked dominant disorders are caused by mutations on the X chromosome
    2. Males and females are both affected by such disorders. However, males are affected more severely
    3. For a man with a X-linked dominant disorder, his sons will all be unaffected (since they receive their father’s Y chromosome) while his daughters will all be affected (since they receive his X chromosome)
    4. A woman with a X-linked dominant disorder has a 50% chance of passing it on to progeny
    5. Eg: Hypophosphatemic rickets, Rett syndrome, Aicardi syndrome
  4. X-linked recessive

    X-linked recessive with a carrier mother

    X-linked recessive with a carrier mother

    1. Caused by mutations on the X-chromosome
    2. Males are affected more frequently than females
    3. The sons of a man affected by a X-linked recessive disorder will not be affected, while his daughters will carry one copy of the mutated gene
    4. The sons of a woman affected by a X-linked recessive disorder will have have a 50% chance of being affected by the disorder, while the daughters of the woman have a 50% chance of becoming carriers of the disorder
    5. Eg: colour blindness, muscular dystrophy, hemophilia A
  5. Y-linked disorders
    1. Caused by mutations on the Y chromosome
    2. Y chromosomes are present only in males
    3. The sons of a man with Y-linked disorders will inherit his Y chromosome and will always be affected while the daughters will inherit his X chromosome and will never be affected
    4. Eg: male infertility
  6. Mitochondrial disorders
    1. These disorders are caused by mutations in the mitochondrial DNA
    2. Only mothers can pass on mitochondrial disorders to children, since only egg cells (from the mother) contribute mitochondria to the developing embryo
    3. Eg: Leber’s Heriditary Optic Neuropathy

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PREVIOUS WEEK: OPTICS, FERTILIZERS, GENETICS
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NEXT WEEK: PARTICLE PHYSICS, CERAMICS, GENETIC ENGINEERING

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PHYSICS: OPTICS IN EVERYDAY LIFE

Working of the Human Eye

  • Light entering the eye passes through the cornea and the pupil
  • Then, the lens focuses light onto an array of photoreceptor cells in the back of the eye, called the retina
  • There are two types of photoreceptor cells:
    • Rod cells: they are responsible for black and white vision, night vision and peripheral vision. They are more in number
    • Cone cells: they are responsible for colour vision. They are less numerous in number

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Defects in vision

  • Presbyopia: as people age, the lens becomes less flexible and near point recedes from the eye. As a result objects far away cannot be see. Can be corrected using a converging lens
  • Hyperopia: lens cannot decrease focal length to focus on nearby objects and so nearby objects cannot be see. Corrected using a converging lens
  • Myopia: lens cannotincrease focal length to  focus on far away objects and so farther objects cannot be seen. Corrected using a diverging lens
  • Astigmatism: occurs when the cornea is not spherical but instead elongated. Results in distorted images. Corrected using a cylindrical surface lens

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Applications of Mirrors

  • Kaleidoscope: A toy in which multiple images are formed by two mirrors placed inside a tube
  • Periscope: Two plane mirrors fixed facing each other  45 degrees. Used in submarines
  • Concave mirror: When used close to face gives magnified image. Used for shaving, personal care etc
  • Convex mirror: Produces smaller image but gives wider range of view. Used in rear view mirrors
  • Parabolic mirror: A concave mirror whose section is the shape of a parabola, helps in focusing. Used as reflectors in search lights, car head lights etc

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Optical instruments and their applications

Instrument Working principle Applications
Microscope Convex lens (converging lens) system consisting of very short focal length eyepiece and longer focal length objective Magnifying tiny objects: molecular studies
Telescope Convex lens system that provides regular magnification Magnifying distant objects: astronomy
Binocular Pair of telescopes mounted side-by-side General use
Interferometer Superposition of waves To study interference properties of light
Photometer Uses a light sensitive element (like photomultiplier) to measure light intensity Used to measure reflection, scattering, fluorescence etc
Polarimeter Light from a source passing through a polarizer and then measured Measures dispersion or rotation of polarized light
Spectrometer Works by measuring light intensity Used to measure light properties: astronomy
Autocollimator Projects and image onto a target mirror and measures deflection of returned image Component alignment, measure deflection in optomechanical systems

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Optics in the atmosphere

Observed effect Underlying cause Description
Blue colour of sky Rayleigh scattering Higher frequencies (blue light) get more scattered than lower frequencies
Red colour of sunrise and sunset Mei scattering Scattering due to suspended particles (like dust) when sun’s rays have to travel longer distance
Halos/afterglows Scattering Scattering off ice particles
Sundog Scattering Scattering off ice crystals causing bright spots on the sky
Mirage Refraction
Novaya Zemlya effect Refraction Sun appears to rise earlier than predicted
Fata Morgana Refraction due to temperature inversion Objects beyond the horizon can be seen elevated
Rainbow Total internal reflection

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Optics for photography

Desired effect Approach
Close up Use macro lens
Long shot Telephoto lens
Panoramic pictures Wide angle lens
Handle low light conditions Increase exposure time (decrease shutter speed)
Fast moving objects Decrease exposure speed (increase shutter speed)
Increase depth of field (foreground and background both in focus) Increase aperture i.e. f-number

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Optical Fibres

  • Optical fibres are glass or plastic fibre that carries light
  • Advantages include
    • low signal loss
    • immunity from electromagnetic interference
    • higher bandwidth (data rate)
    • low power consumption
  • Optical fibres work on the principle of Total Internal Reflection
  • Applications include long distance communication, endoscopy, light decorations etc

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CHEMISTRY: FERTILIZERS AND PESTICIDES

FERTILIZERS

About fertilizers

  • Fertilizers are soil amendments applied to promote plant growth
  • Can be applied to soil or directly to leaves
  • Main nutrients in a fertilizer are nitrogen, phosphorous and potassium

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Synthetic fertilizers

  • Synthetic fertilizers are manufactured using the Haber-Bosch process to produce ammonia, which is then used to manufacture other nitrogen fertilizers
  • Urea is the most commonly used fertilizer. It has the highest nitrogen content
  • Synthetic fertilizers do not replace trace minerals in the soil (eg Zinc, copper, magnesium etc)
  • Production of synthetic fertilizers is highly energy intensive. The production of synthetic ammonia currently accounts for 5% of global natural gas consumption
  • Excess and unregulated use of synthetic fertilizers can cause Fertilizer Burn, in which plant tissues die due to excess nitrogenous salts

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Biofertilizers

  • Include naturally occurring minerals such as manure, worm castings, compost, etc.
  • Primary sources of biofertilizers are
    • Bacteria: Rhibozium, Azopirillum
    • Fungi: Mycorrhiza
    • Fern: Azolla
  • Cover crops can also be used to enrich soil between plantings of the main crop. Cover crops work through the principle of nitrogen fixation: i.e. convert atmospheric nitrogen into a plant-accessible form
  • Minerals such as limestone, rock phosphate and sulphate of potash can also be used
  • Biofertilizers release their nutrients much slowly compared to synthetic fertilizers and thereby prevent Fertilizer Burn
  • In addition to improving crop yields, biofertilizers also improve the health and long-term productivity of soil

Keywords: ias, upsc, civil service, study material, general studies

Environmental effects of fertilizer use

  • Oxygen depletion: Nitrogen compounds in fertilizer run-off are primarily responsible for serious oxygen depletion in oceans and lakes. This lack of dissolved oxygen causes serious damage to aquatic life in lakes and along coastal areas. Also leads to discolouration of water (green, yellow, red, brown)
  • Soil acidification: Nitrogen containing synthetic fertilizers cause soil acidification
  • Heavy metal accumulation: Synthetic fertilizers, especially those based on phosphates, can contain significant amounts of cadmium, uranium, zinc, lead and radioactive polonium, all of which can be stored in plant tissues, and later enter the food chain in the form of produce
  • Greenhouse gases: Due to the large scale use of fertilizers, nitrous oxide has now become the third most important greenhouse gas (after carbon dioxide and methane).

Keywords: ias, upsc, civil service, study material, general studies

PESTICIDES

Overview

  • A pesticide is a substance that is used to kill pests
  • Pests can include insects, molluscs, birds, weeds etc
  • In addition to preventing crop losses due to pests, pesticides can kill disease-spreading mosquitoes, allergy inducing bees or wasps, and also to control algae levels in lakes
  • Due to its negative effects on birds, DDT has been banned as a pesticide for agricultural use under the 2001 Stockholm Convention. However, it is still used in developing countries for malaria prevention and other vector control

Keywords: ias, upsc, civil service, study material, general studies

Commonly used pesticides

Pesticide

Used to control

Example
Algaecide

Algae

Copper sulphate, barley straw
Avicide

Birds

Strychnine, DRC1339, parathion (in diesel oil)
Bactericides

Bacteria

Chlorine, iodine, oxygen, alchohol, phenol
Fungicide

Fungi, oomycete (water molds)

Sulphur, neem oil, tea tree oil, rosemary oil, milk
Herbicide

Weeds

Dichlorophenoxyacetic acid (2,4D), atrazine, glyphosate
Insecticide

Insects

Organochlorine, organophosphates, carbamates, pyrethroids
Miticide

Mites

Methoprene, permethrin, dicofol
Molluscicides

Molluscs (slugs and snails)

Metal salts (iron phosphate, aluminium sulphate), metaldehyde
Nematicide

Nematodes (worms)

Nematophagus fungi, neem cake
Rodenticide

Rodents

Anticoagulants, metal phosphides, hypercalcemia

Keywords: ias, upsc, civil service, study material, general studies

Environmental effects of pesticides

  • Over 98% of insecticides and 95% of herbicides reach a destination other than their target species
  • Pesticides contaminate land and water when they run-off from fields, when discarded, sprayed etc
  • Air pollution: pesticide drift occurs when pesticides suspended in the air get carried away to other areas. Pesticides also react with other chemicals to produce ozone, accounting for about 6% of total ozone production
  • Water pollution: run-off and eroding soil lead to pesticide pollution of water. This affects water solubility, and also the pesticides enter the food chain through water. Some pesticides are toxic to fish, kill off zooplankton (the main food source for fish). Harmful to amphibians such as tadpoles and frogs
  • Soil contamination: nitrogen fixation is affected by pesticides in soil. Pesticides also kill bees and are responsible for pollinator decline, leading to decreased crop yields. Widespread use of pesticides eliminates animals’ food sources causing them to change food habits or starve. Pesticide poisoning also travels up the food chain

Keywords: ias, upsc, civil service, study material, general studies

Pest resistance and rebound

  • Pests may evolve to become resistant to pesticides
  • Managed through pesticide rotation
  • Mixture of pesticides may also be used
  • Certain pests sometimes themselves act as pesticides in the sense that they control other pests. In this case pesticides that target one pest species may lead to a secondary pest outbreak due to the other species
  • Also, sometimes use of pesticides may affect natural enemies of the pest more than the pest itself. In this case, the pesticide may lead to temporary decrease in pest populations, but in the long-term the pest population may increase due to the absence of its natural enemies (especially for mosquitoes). This is called pest rebound.

BIOLOGY: GENETICS

History of genetics research

  • The father of genetics is Gregor Mendel (Austria-Hungary). In 1866 he published the principle known as Mendelian Inheritance which described the concept of inheritance between parent organisms and offspring
  • In 1869 Friedrich Miescher (Switzerland) discovered DNA
  • 1880: Walther Flemming (Germany) describes division of chromosomes
  • 1933: Jean Brachet (Belgium) establishes DNA is found in chromosomes and RNA in cell cytoplasm
  • 1944: Oswald Theodore Avery, Colin McLeod, Maclyn McCarty (US) identify DNA as genetic material
  • 1953: James Watson and Francis Crick (US) establish double helix structure of DNA. They win the Nobel Prize in Physiology or Medicine in 1962 for this discovery
  • 1968: Hargobind Khorana, Robert Holley and Marshall Nirenberg (US) demonstrate the role of RNA in protein synthesis. Nobel in Medicine 1968
  • 1977: Frederick Sanger (UK) sequences DNA for the first time. He produce the entire genome of bacteriophage X174. Nobel in Chemistry in 1980
  • 1983: Kary Mullis (US) discovers polymerace chain reaction enabling easy amplification of DNA. Nobel in Chemistry 1993
  • 1995: The genome of Haemophilus influenzae is the first genome of a living organism to be sequenced
  • 2001: First draft sequence of the human genome
  • 2003: Human Genome Project successfully completed

DNA

  • DNA (deoxyribonucleic acid) is the basis for genetic inheritance. However, certain viruses use RNA for genetic information
  • DNA is composed of a chain of nucleotides. There are four types of nucleotides: adenine (A), cytosine (C), guanine (G), thymine (T)
  • DNA usually exists in a double-helix structure molecule
  • Each nucleotide in one strand of the double-helix pairs with a particular partner nucleotide in the other strand. A pairs with T and C pairs with G

Chromosome

  • Genes are regions within DNA. Genes are arranged in long chains of DNA molecules. These chains are called chromosomes
  • Eukaryotic organisms have DNA arranged in multiple such chromosomes. Bacteria have only one chromosome
  • The combined DNA sequence of all chromosomes is called the genome. This contains all hereditary information of that organism
  • Haploid organisms have only copy of each organism. Eg: male bees, wasps, ants
  • Diploid organisms have two copies of each chromosome. Eg: most plants and animals (including humans). However, in male humans the sex-linked X and Y chromosomes exist only as a single copy.
  • Male: XY, Female: XX

Human Genome Project

  • The Human Genome Project was an international scientific effort to determine the complete genetic code of human beings
  • Launched in 1990, complete results published in 2003
  • Performed by scientists from US, UK, Canada and New Zealand, lead by University of California Santa Cruz
  • Key findings of the project include
    • There are approximately 25000 genes in human beings
    • All human races are 99.99% alike genetically
    • Most genetic mutation occurs in male. Thus males are responsible for genetic evolution and for genetic disorders
  • Human Genome Project mapped nucleotides in haploid sequences. Efforts are currently underway to map diploid sequences as well. Eg: International HapMap Project, Personal Genome Project

Keywords: ias, upsc, civil service, study material, general studies

Previous Week: Waves, Radioactivity and Biomolecules ~~~~~~~~~Next Week: Nuclear Physics, Polymers and Genetic Disorders

8 December 2009 | Tags: , , , | 1 Comment »

General Science #4 | Study Material :: General Studies | IAS Help

PHYSICS: WAVES

Overview

  • A wave is a disturbance that travels across space and time
  • Propagation of waves usually involves transference of energy without transferring mass. This is achieved by oscillations or vibrations around fixed locations
  • Mechanical waves require a medium for transmission (e.g. sound)
  • Electromagnetic waves do not require a medium and can travel in vacuum (e.g. light)
  • Longitudinal waves are those with vibrations parallel to the direction of wave propagation. E.g. sound waves
  • Transverse waves are those with vibrations perpendicular to the direction of travel. E.g. electromagnetic waves including light
  • Waves on a string are an example of transverse waves

Keywords: ias, study material, general studies, general science

Properties of waves

  1. Reflection: It is the change in direction of a wave at the interface between two media. Examples include reflection of light, sound etc
  2. Refraction: It is the change in direction of a wave due to a change in its speed. Examples: refraction of light when it passes through a lens
  3. Diffraction: Bending of waves as they interact with obstacles in their path. Example: rainbow pattern when light falls on a CD or DVD
  4. Interference: Superposition of two waves that come into contact
  5. Dispersion: the splitting up of waves by frequency
  6. Polarization: the oscillation of a wave in only one direction. Exhibited only by transverse waves (like light), not exhibited by longitudinal waves (like sound)

Keywords: ias, study material, general studies, general science

Wave properties in everyday life

  • The floor of a lake or the ocean appears closer than it actually is. This is because of refraction of light
  • The red ring around the Sun is due to diffraction of light
  • We can hear but not see across corners, this is because of diffraction of sound (e.g. we can hear but not see a person in the next room)
  • The rainbow and the blue colour of sky are both due to dispersion of light
  • Sunglasses use polarization filters to block glare

Keywords: ias, study material, general studies, general science

SOUND WAVES

About Sound

  • Sound is a mechanical wave that is transmitted as longitudinal waves through gases, plasma and liquids. However, in solids it can travel as both longitudinal and transverse waves
  • Sound cannot travel in vacuum, it needs a medium for propagation
  • The speed of sound in air is 330 m/s

Keywords: ias, study material, general studies, general science

Perception of sound

  • The frequency range 20 Hz to 20 MHz is known as the audible range, where human beings can detect sound waves
  • The upper frequency limit decreases with age i.e. as we get older, our ability to detect higher pitches (shrills) decreases
  • Other species uses different ranges for hearing. E.g. dogs can perceive frequencies higher than 20 KHz
  • Increased levels of sound intensity can cause hearing damage. Hearing can be damaged by sustained exposure to 85 dB or by short term exposure to 120 dB sound. A rocket launch usually involves about 165 dB

Keywords: ias, study material, general studies, general science

Sonar systems

  • Sound Navigation and Ranging is a technology that uses sound propagation for navigation and communication
  • Primarily used under water because light attenuates very quickly in water whereas sound travels farther
  • First developed by R.W. Boyle and A.B. Wood in 1917 in Britain
  • Applications include military, fisheries, wave measurement, ocean-floor mapping etc
  • Sonar is used by marine mammals (like dolphins and whales) for communication as well
  • Bats communicate by means of SONAR at frequencies over 100 MHz (beyond the human range)

Keywords: ias, study material, general studies, general science

ELECTROMAGNETIC WAVES

Electromagnetic Spectrum


Keywords: ias, study material, general studies, general science

Electromagnetic radiation and applications

Radiation

Applications
Radio waves

RADAR, TV, cell phones, microwaves
Microwaves

Wi-Fi
Infrared (IR)

Night vision, thermography, imaging
Visible light

Sight
Ultraviolet (UV)

Sun burn, water disinfection
X-rays

Astronomy, medicine
Gamma rays

PET scans, cancer therapy, astronomy, food sterilization

Keywords: ias, study material, general studies, general science

Radar systems

  • Radio Detection and Ranging is a technology that uses radio waves to identify moving and fixed objects
  • Developed by Robert Watson-Watt in 1935 in Britain
  • Radar works by measuring the waves that are reflected back from an object. Radar can detect objects at ranges where sound or visible light would be too weak
  • Applications include aircraft detection, air traffic control, highway speed detection, weather detection etc

Keywords: ias, study material, general studies, general science

More about electromagnetic waves

  • Radio waves are reflected by the ionosphere and hence can be received anywhere on the earth.
  • TV transmission penetrates the ionosphere and hence is not received like radio waves. Thus TV transmission is limited to line-of-sight
  • At night, the radio reception improves because the ionosphere is not exposed to sunlight and hence is more settled
  • Bats communicate by means of SONAR at frequencies over 100 MHz (beyond the human range). Other animals like dolphins and whales use SONAR as well

Keywords: ias, study material, general studies, general science

CHEMISTRY: RADIOACTIVITY

About radioactivity

  • It is the process by which an unstable atomic nucleus spontaneously decays (loses energy) by emitting ionizing particles and radiation
  • This decay results in the atom of one type (parent nuclide) transforming into an atom of a different type (daughter nuclide)
  • Eg: Carbon-14 emits radiation and transforms into nitrogen-14
  • The SI unit of radioactivity is Becquerel (Bq). Another commonly used unit is the Curie (Ci)
  • Radioactivity of a material is quantified by its half life. This is the time taken for a given amount of a radioactive material to decay to half its initial value
  • Radiation can be measured using scintillation counters and Geiger counters

Keywords: ias, study material, general studies, general science

History of radioactivity research

  • Radioactivity was first discovered by French scientist Henri Becquerel in 1896
  • Research in radioactivity of uranium led Marie Curie to isolate a new element Polonium and to separate Radium from Barium
  • The dangers of radioactivity was discovered by Nikola Tesla in 1896, when he intentionally subjected his fingers to X-rays
  • Henri Joseph Muller was awarded the Nobel Prize in Physiology or Medicine in 1946 for his discovery (in 1927) of the harmful genetic effects of radiation

Keywords: ias, study material, general studies, general science

Transmutation of elements

  • Isotopes: they are atoms of an element with the same atomic number but different mass number (eg uranium-238 and uranium-235)
  • Isobars: elements with same mass number but different atomic number. Usually occurs when a radioactive nucleus loses a beta particle (eg. Thorium-234 and palladium-234)
  • Isotones: radioactive nuclei that contain the same number of neutrons (eg. Radium-226 and Actium-227)
  • Isomers: are different excitation states of nuclei. The higher-energy (unstable) element undergoes isomeric transition to form the less energetic variant without change in atomic or mass number

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Types of radioactive decay

Alpha rays can be stopped by a sheet of paper, beta rays by aluminium shielding, while gamma rays can only be reduced by a thick layer of lead

Alpha rays can be stopped by a sheet of paper, beta rays by aluminium shielding, while gamma rays can only be reduced by a thick layer of lead

  • Radioactive radiation can be split into three types of beams
  • Alpha rays: they are helium particles that carry a positive charge. They have low energy and can be stopped by a sheet of paper
  • Beta rays: they are streams of electrons and carry negative charge. They have higher energy than alpha rays
  • Gamma rays: they are high energy rays (like X-rays) that carry no electrical charge

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Radioactivity and the Big Bang theory

  • According to the Big Bang theory stable isotopes of the lightest elements (H, He, Li, Be, B) were formed immediately after the Big Bang
  • Radioactive (unstable) isotopes of these light elements have long since decayed, and isotopes of elements heavier than boron were not produce at all in the Big Bang
  • Thus, the radioactive materials currently in the universe were formed later and are relatively young compared to the age of the universe
  • These radioactive nuclei were formed in nucleosynthesis in stars and during interactions between stable isotopes and energetic particles
  • For instance, carbon-14 is constantly produced in the earth’s upper atmosphere due to interactions between cosmic rays and nitrogen

Keywords: ias, study material, general studies, general science

Applications of radioactivity

  • Radioisotopic labeling: used to track the passage of a chemical through the human body. Some common radio isotopes used for labeling are
    • Tritium: used to label proteins, nucleic acids
    • Sodium-22 and Sodium-36: ion transporters
    • Sulphur-35: proteins and nucleic acids
    • Phosporous-32 and Phosphorous-33: nucleotides (like DNA)
    • Iodine-125: thyroxine
    • Carbon-14 is not used for radioactive labeling due to its long half life (5730 years)
  • Random number generators: based on the premise that radioactive decay is truly random
  • Radiometric dating: used to date materials based on a comparison between observed abundance of radioactive isotopes and its decay products, using known decay rates. The most common methods of radiometric dating are
    • Carbon dating: when organic matter grows, it traps carbon-14. The age of the organic matter can be estimated by measuring the amount carbon-14 remaining in the body. Used for dating material up to 60,000 years old
    • Potassium-argon dating: used in geochronology and archeology, especially for dating volcanic material. Used for samples older than a few thousand years
    • Uranium-lead: one of the oldest and most refined radiometric dating techniques. Used in geochronology to estimate material from 1 million to 4.5 billion years old. A variant, the lead-lead dating scheme was used by American scientist Clair Cameron Patterson to estimate the age of the earth (4.55 billion years) in 1953

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Radioactive therapy

  • Used for palliative and therapeutic treatment
  • Common applications include treatment of thyroid eye disease, heterotopic ossification, trigeminal neuralgia
  • In low doses, it is used for cancer treatment. However, in large doses, it can cause cancer
  • Total body irradiation is used to prepare the body to receive a bone marrow transplant

Keywords: ias, study material, general studies, general science

Radiation poisoning

  • It is a form of damage to organ tissue due to excessive exposure to ionizing radiation
  • Caused by exposure to large doses of radiation in short periods of time, or by exposure to small doses over long periods
  • Increases the probability of contracting other diseases like cancers, tumours and genetic damage
  • Common symptoms are nausea and vomiting
  • Common occurrances of radiation poisoning include nuclear warfare, nuclear reactor accidents, spaceflight (exposure to cosmic rays), ingestion and inhalation of radioactive compounds (such as strontium in cow’s milk)
    • In Nov 2006, Russian dissident died due to suspected deliberate ingestion of Polonium-210

BIOLOGY: BIOMOLECULES

  1. Lipids
    • They are a broad group of molecules that include fats, fatty acids, sterol, waxes, glycerides and phospholipids
    • Fats are a subgroup of lipids called triglycerides
    • Cholesterol is an example of the type of lipids called sterol
    • The main functions of lipids include energy storage, cell signaling and cell structure
  2. Carbohydrates
    • They are organic compounds that contain only carbon, hydrogen and oxygen
    • They belong to 3 types: monosaccharides, disaccharides and polysaccharides
    • Monosaccharides
      • Monosaccharides are the simplest form of carbohydrates, and cannot be broken down any further.
      • Eg: glucose and fructose
      • Monosaccharides dissolve in water, taste sweet and are called “sugars”
      • Used as energy source and in biosynthesis
    • Disaccharides
      • Disaccharides are compounds made by two monosaccharides bound together.
      • Eg: sucrose and lactose
      • Like monosaccharides, disaccharides dissolve in water, taste sweet and are called “sugars”
      • Used for carbohydrate transport
    • Polysaccharides
      • Polysaccharides are compounds made by complex chains of monosaccharides.
      • Eg: cellulose, glycogen
      • Used for energy storage (glycogen) and for cell walls (cellulose)
      • Cellulose is the most abundant organic molecule on Earth
  3. Amino acids
    • They are molecules that contain an amine group and a carboxyl group
    • Eg: glycine, monosodium glutamate
    • They are the building blocks of proteins
    • Applications include metabolism, drug therapy, flavour enhancement, manufacture of biodegradble plastics
  4. Proteins
    • They are compounds made from amino acids
    • The first protein to be sequenced was insulin, by Frederick Sanger who won the Nobel Prize in Chemistry for this in 1958
    • The first protein structures to be solved were hemoglobin and myoglobin by Max Perutz and Sir John Cowdrey Kendrew in 1958. They won the Nobel Prize in Chemistry for this achievement in 1962
    • Proteins are used as enzymes, in muscle formation, as cell cytoskeleton, cell signaling and immune responses
    • The process of digestion breaks down protein into free amino acids that are then used in metabolism
  5. Nucleic acids
    • They are macromolecules formed by chains of nucleotides
    • Common examples include DNA and RNA
    • DNA (Deoxyribonucleic acid)
      • Contains two strands of nucleotides arranged in a double helix structure
      • In cells, DNA is organized into long structures called chromosomes
      • Used primarliy for long term storage of genetic information
      • DNA was first isolated by Swiss physician Friedrich Miescher in 1869
      • The double helix structure was suggested by James Watson and Francis Crick in 1953. They, alongwith Maurice Wilkins won the Nobel Prize in Physiology or Medicine for this discovery in 1962
    • RNA (ribonucleic acid)
      • Contains one strand of nucleic acids
      • Less stable than DNA
      • Used primarily for protein synthesis
      • Messenger RNA carries information from DNA to the ribosome. Translation RNA translates the information in the mRNA
      • RNA synthesis was discovered by Severo Ochoa of Spain, for which he won the Nobel Prize in Physiology or Medicine in 1959

Matching cell functions to biomolecules

Function

Biomolecule

Cell structure

Lipid

Impact protection

Lipids and proteins

Enzymes

Proteins

Energy storage

Carbohydrates, proteins, lipids

Cell movement and support

Proteins (actin and myosin)

Protein synthesis

Nucleic acids (RNA)

Hormones

Proteins

Immediate cellular energy

Carbohydrates (glucose)

Electrical and thermal insulation

Lipids

Storage of amino acids

Proteins

Genetic information

Nucleic acids (DNA)

Keywords: ias, study material, general studies, general science, physics, chemistry, biology

1 December 2009 | Tags: , , | 1 Comment »

General Science #3 | Study Material :: General Studies | IAS Help

PHYSICS: HEAT

Overview

  • Heat is the process of energy transfer from one system to another
  • Units of heat: Joules (J), Calories, British Thermal Unit (BTU)
  • Temperature is a measure of internal energy (enthalpy)
  • Heat transfer can happen spontaneously only from a warmer to a colder body. Reverse heat transfer can only happen with the aid of an external source such as a heat pump.

Mechanisms of heat transfer

  • Conduction is the most significant heat transfer mechanism in solids. It occurs as hot high energy molecules interact with neighbouring and transfer heat to them. Eg: heat transfer from one end of a metal rod to another
  • Convection is most significant in liquids and gases. This happens when hot molecules move and transfer energy to other molecules. Eg: boiling of water. When water is heated on a stove, hot water from the bottom rises and displaces colder liquid which falls.
  • Radiation is the only form of heat transfer possible in the absence of a medium. Heat is transferred in the form of electromagnetic radiation. Eg: heat from the sun reaching the earth.

Heat transfer in everyday life

  • Copper is used in construction of boilers and cooking utensils because it is a good conductor of heat
  • Air is a poor conductor
  • Wool and cotton are good insulators i.e. poor conductors. Their insulation arises mainly due to air spaces between molecules
  • Double-walled glass doors with air between them are better insulators than windows with a single thick glass layers
  • Eskimos live in snow huts because snow is a poor conductor of heat, and hence protects them from the extreme cold outside.
  • Land and sea breeze, ocean currents are arise due to convection
  • The boiling point of water at sea level and atmospheric pressure is 100C. When extra heat is added, it changes the phase of water from liquid to gas (water vapour).

Thermometers

  • Thermometers can be divided into two groups:
    • Primary thermometers: measure temperature directly based on the property of matter. They are relatively complex and not used commonly. Eg: thermometers based on velocity of sound in gas, thermal noise of an electrical resistor etc.
    • Secondary thermometers: measure temperature relative to a pre-calibrated quantity. They are easy to use and used commonly. Alcohol thermometer, mercury thermometer, medical thermometer are all secondary thermometers
  • In cold winter places, alcohol thermometers are used instead of mercury thermometers because the freezing point of alcohol is lower
  • For extra-low temperature measurements (-200 C), Pentane is used
  • Water is not suitable for use in thermometers because it freezes at 0 C and has irregular expansion
  • Mercury is used for common medical thermometers because
    • It does not cling to glass and hence reading is easy
    • It is opaque and easily seen
    • Its expansion is uniform and hence calibration is easier
    • It is a better conductor of heat than alcohol and hence responds more rapidly to changes of temperature
    • It has low specific heat capacity and hence is more sensitive

Common appliances based on heat

  • Solar cooker: is a box made of insulating material such as wood, cardboard etc. The box has a glass cover to retain heat inside by greenhouse effect. The inside of the box is painted black to increase heat absorption.
  • Pressure cooker: Pressure cooker increases the boiling point of water by increasing pressure. When the boiling point of water increases, food cooks faster. Pressure cookers are especially essential in hill stations because at higher altitudes the boiling point of water decreases due to lower atmospheric pressure
  • Refrigerator and Air-conditioner: are heat pumps that transfer heat from inside to the external environment. They use a refrigerant which is a compound that undergoes reversible phase change from gas to liquid. Common refrigerants include ammonia, sulphur dioxide, carbon dioxide and methane. The use of chlorofluorocarbons has been phased out due to concerns regarding depletion of the ozone layer.

CHEMISTRY: ELECTROLYTES

Electrolytes in the human body

  • Electrolytes are required in the body to maintain balance between intracellular and extracellular liquids. In particular, it is important to maintain the osmotic gradient between inside and outside.
  • Electrolyte balance is maintained by oral and intravenous intake
  • Kidneys flush out excess electrolytes
  • Dehydration and overhydration are caused by electrolyte imbalance
  • Hormones that maintain electrolyte balance are antidiuretic hormone, aldosterone and parathyroid hormone
  • The most common electrolyte in the body is salt (sodium chloride)

Functions of electrolytes in the body

  • Maintain blood pH
  • Muscle and neuron activation
  • Hydration of the body

Other common applications of electrolytes

  • Sports drinks
  • Batteries
  • Fuel cells
  • Electroplating
  • Capacitors

Sports Drinks

  • Sports drinks replenish the body’s water and electrolyte levels after dehydration caused by exercise, vomiting, diarrhea etc.
  • They are made of electrolytes containing sodium and potassium salts
  • Examples of sports drinks: Glucon-D, Gatorade etc
  • Simplest electrolyte drink that can be made at home is water + sugar + salt

Batteries

Battery

Electrode

Electrolyte

Other notes
Alkaline

Zinc, Manganese oxide

Potassium Hydroxide
Daniell cell

Copper, Zinc

Copper sulphate, zinc sulphate
Leclanche cell

Zinc, carbon

Ammonium chloride

Precursor of modern dry cell
Voltaic pile

Copper, zinc

Brine

First electric battery, invented in 1880
Zinc carbon

Zinc, carbon, manganese dioxide

Zinc chloride, ammonium chloride

Most common battery
Zinc chloride

Same as above

Zinc chloride

Improvement on zinc carbon battery
Lead-acid

Lead, lead dioxide

Sulphuric acid

Oldest rechargeable battery

Used in vehicles as they provide high surge currents
Lithium-ion

Graphite, Lithium Cobalt oxide

Non-aqueous lithium salts

Rechargable

Slow self-discharge, high energy to weight ratio
Nickel Cadmium

Nickel oxide hydroxide, cadmium

Rechargable

Last longer, more stable than lithium ion
Fuel cell

Hydrogen (fuel), oxygen (oxidant)

Polymer membrane

Aqueous alkaline solution

Consumes reactant from an external source

High energy efficiency and high reliability

No moving parts

Used in space shuttles, submarines

Common electrolytes and their uses

Electrolyte

Uses

Other notes
Sodium chloride

Primary component of extracellular fluid

Food preservative
Sodium hydroxide

(caustic soda)

Manufacture of paper, soaps, detergents, drain cleaners

Purification of drinking water
Silver nitrate

Photographic films

Water disinfection (esp. on space shuttles)
Hydrochloric acid

Manufacture of PVC, household cleaners

Food additives (like gelatin)

Leather processing

Found naturally in gastric acid
Sulphuric acid

Lead-acid batteries

Ore processing

Fertilizer manufacture

Soluble in water at all concentrations

One of the largest products of chemical industry
Nitric acid

Determining metal traces in solutions

Wood finishing

Colourless when pure, yellows with age

Highly corrosive
Acetic acid

Manufacture of soft drink bottles

Photographic films

Synthetic fibres and fabrics

Dilute acetic acid is called vinegar
Ammonium hydroxide

(aqueous ammonia)

Cleaning agent
Calcium hydroxide

(slaked lime or pickling lime)

Sewage treatment

Whitewash, plaster, mortar

Hair relaxers

Natural mineral form is called portlandite

(rare mineral occurring in volcanic rocks)

BIOLOGY: BLOOD

Overview

  • Blood is a specialized body fluid that delivers necessary substances to various cells (like nutrients and oxygen) and transports waste products away from those cells
  • Blood accounts for 7% of human body weight
  • The average human adult has a blood volume of approx. 5 litres
  • Arteries carry inhaled oxygen-rich blood from the heart to the tissues, while veins carry carbon dioxide rich blood (de-oxygenated) from the tissues to the lungs to be exhaled
Red_White_Blood_cells

SEM image of a RBC, a platelet and a WBC (L to R)

Composition of blood

  • Blood is made of plasma, Red Blood Cells, White Blood Cells (including leukocytes and platelets)
  • Plasma constitutes about 54.3% of blood, RBCs 45% and WBCs about 7%
  • RBCs contain hemoglobin and distribute oxygen to tissues
  • Leukocytes attack and remove pathogens and provide immunity
  • Platelets are responsible for clotting of blood
  • Plasma is the blood’s liquid medium. It circulates dissolved nutrients and removes waste products. By itself, it is yellow in colour

Functions of blood

  • Supply oxygen to tissues
  • Supply nutrients such as glucose, amino acids and fatty acids
  • Remove waste such as carbon dioxide, urea and lactic acid
  • Provide immunity against pathogens
  • Coagulation
  • Transport hormones
  • Regulate pH
  • Regulate core body temperature

Colour of blood

  • Colour is primarily determined by hemoglobin
  • Arterial blood is bright red, due to the presence of oxygen
  • Venous blood is dark red, due to deoxygenation
  • Blood in carbon monoxide and cyanide poisoning is bright red
  • Blood of most molluscs (marine animals like squids, oysters, snails, octopuses etc) is blue due to the presence of copper containing protein hemocyanin

Blood Groups

Blood Group

Can donate to

Can receive from
A

A and AB

A and O
B

B and AB

B and O
AB

AB only

All groups
O

All groups

O only

Medical disorders related to blood

Disorder

Cause

Other notes
Bleeding

An adult can lose 20% of blood volume before the first symptom (restlessness) sets in
Dehydration

Loss of volume due to loss of water
Atherosclerosis

Reduced blood flow through arteries
Thrombosis

Coagulation of blood vessels
Hypoxia (lack of oxygen)

Narrowing of blood vessels

Problem with pumping action of heart

Can lead to ischemia (tissue with insufficient blood) or to infarction i.e. necrosis (tissue death)
Anemia (insufficient RBC)

Bleeding, nutritional deficiencies
Sickle-cell disease

Mutation of hemoglobin leading to abnormal sickle shape of RBC

Sickle shaped RBCs do not have the flexibility to travel through many blood vessels

Extremely painful disease with no known cure

Found commonly in malaria-infested areas because sickle cells offer resistance to malaria
Leukemia

Abnormal proliferation of WBCs in the bone marrow
Hemophilia

Dysfunction of clotting mechanism

Lack of coagulation means simple wounds become life-threatening

Causes hemarthosis (bleeding into joints), which is painful and crippling

Linked to X chromosome

Occurs usually in males only
Thrombophilia

Abnormal propensity to coagulate
Blood-borne infections

Infection by a disease-carrying vector

Examples: HIV, Hepatitis, Malaria
Carbon monoxide poisoning

Carbon monoxide binds to hemoglobin preventing oxygen transport

Body tissues die due to lack of oxygen
24 November 2009 | Tags: , , | 1 Comment »
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