General science Biology-3

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)

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
  

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

General science Biology-2

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

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)

      BIOLOGY: GENETIC DISORDERS
      

      About genetic disorders
      
      

      Huntington's disease is inherited in the autosomal dominant fashion
      
      
   3. Genetic disorders are disorders that are passed on from generation to generation
   4. They are caused by abnormalities in genes or chromosomes
   5. Some genetic disorders may also be influenced by non-genetic environmental factors. Eg: cancer
   6. Most genetic disorders are relatively rare and only affect one person in thousands or millions
   7. To recollect, males have XY chromosome pairs while females have XX pairs
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   Single Gene Disorders
   
   
5. Single gene disorders result from the mutation of a single gene
6. They can be passed onto subsequent generations in multiple ways
7. 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

   
   
   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

   
   
   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

      BIOLOGY: GENETICS

      History of genetics research
      
   4. 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
   5. In 1869 Friedrich Miescher (Switzerland) discovered DNA
   6. 1880: Walther Flemming (Germany) describes division of chromosomes
   7. 1933: Jean Brachet (Belgium) establishes DNA is found in chromosomes and RNA in cell cytoplasm
   8. 1944: Oswald Theodore Avery, Colin McLeod, Maclyn McCarty (US) identify DNA as genetic material
   9. 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
   10. 1968: Hargobind Khorana, Robert Holley and Marshall Nirenberg (US) demonstrate the role of RNA in protein synthesis. Nobel in Medicine 1968
   11. 1977: Frederick Sanger (UK) sequences DNA for the first time. He produce the entire genome of bacteriophage X174. Nobel in Chemistry in 1980
   12. 1983: Kary Mullis (US) discovers polymerace chain reaction enabling easy amplification of DNA. Nobel in Chemistry 1993
   13. 1995: The genome of Haemophilus influenzae is the first genome of a living organism to be sequenced
   14. 2001: First draft sequence of the human genome
   15. 2003: Human Genome Project successfully completed
   DNA
   
7. DNA (deoxyribonucleic acid) is the basis for genetic inheritance. However, certain viruses use RNA for genetic information
8. DNA is composed of a chain of nucleotides. There are four types of nucleotides: adenine (A), cytosine (C), guanine (G), thymine (T)
9. DNA usually exists in a double-helix structure molecule
10. 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

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General science Biology-1

BIOLOGY

HISTORY OF CELL STUDIES

1. 1665: Robert Hooke discovers cells in cork
2. 1839: Theodor Schwan and Matthias Jakob Schleiden found cell theory
3. 1931: Ernst Ruska builds first Transmission Electron Microscope at the University of Berlin
4. 1953: Watson and Crick discover double helix structure of DNA. They, along with Maurice Wilkins, won the Nobel Prize in Physiology or Medicine in 1962

GENETIC MATERIAL IN A CELL

1. DNA used mainly for storing genetic information
2. RNA used mainly for information transport. Sometimes used for genetic storage in certain viruses
3. Human cell encodes genetic information in DNA
4. Human genetic material found in nuclear genome and mitochondrial genome
5. Nuclear genome divided into 23 pairs of DNA molecules called chromosomes
6. Mitochondrial genome codes for 13 proteins used in mitochondrial energy production

COMPONENTS OF A CELL

1. Cell Membrane
   • Separates interior of a cell from outside environment
   • Semi-permeable
   • Made of proteins and lipids
   • Protein receptors are found on the cell membrane
2. Cytoplasm
   • Part of a cell enclosed withing cell membrane
   • Contains three major elements: cytosol, inclusions, organelles
3. Cytosol
   • Translucent fluid made of water, salts and organic molecules
   • Makes up 70% of cell volume
   • Contains protein filaments (that make up the cytoskeleton) and vault complexes
4. Inclusions
   • Small insoluble particles suspended in cytosol
   • Include energy storage materials such as starch and glycogen
5. Organelles
   • Compartments withing the cell that have specific functions. Eg: mitochondria, golgi apparatus, lysosomes etc
6. Mitochondria and Chloroplasts
   • Both generate energy in the cell
   • Mitochondria uses Oxygen to generate ATP
   • Chloroplasts generate carbohydrates and Oxygen from carbon dioxide and water
   • Mitochondria found in plants and animals. Chloroplasts found only in plants
7. Ribosomes
   • Large complex of RNA and protein molecules
8. Nucleus
   • Contains chromosomes
   • Site of DNA replication and RNA synthesis
     
9. Golgi Apparatus
   • Found in eukaryotes only
   • Process and package proteins and lipids synthesised by a cell
10. Lysosomes and Peroxisomes
    • Lysosomes have digestive enzymes
    • Digest excess or worn-out organelles, food particles, virus/bacteria
    • Peroxisomes have enzymes that rid the cell of toxic peroxides
11. Vacuoles
    • Store food and waste

FUNCTIONS OF A CELL

1. Cell metabolism
   1. Cell metabolism required for cell growth
      
   2. Metabolism is the process by which cells process nutrient molecules
   3. Catabolism: cell produces energy by breaking down complex molecules
      
   4. Anabolism: cell uses energy to construct complex molecules and perform other functions
2. Cell division
   • Required for building tissue and procreation
   • Prokaryotic cells divide by binary fission
   • Eukaryotic cells divide by mitosis or meiosis
   • Mitosis produces two identical daughter cells, meiosis produces two daughter cells each with half the number of chromosomes
   • DNA replication is required every time a cell divides
3. Protein synthesis
   • New proteins formed from amino acids
   • Consists of two steps: transcription and translation

ASK AND TELL…

1. Prokaryotes are
   1. animals without developed nervous systems
   2. organisms lacking nucleus
   3. primitive plants without vascular systems
   4. plants that do not produce flowers and fruits
2. Honey that has high concentration of sugar does not decay because
   1. it contains natural anti oxidants that prevents bacterial attack
   2. bacteria can’t survive in active state in a solution of high osmotic strength as water is drawn out
   3. bacteria can’t survive in active state as it is deprived of oxygen
   4. none of these
3. The number of chromosomes in a bacterium is
   1. 1
   2. 2
   3. 4
   4. varies with species
4. Granum is a component of
   1. chloroplasts
   2. golgi apparatus
   3. ribosomes
   4. starch grains
5. In a plant cell, DNA is found in
   1. chloroplasts
   2. mitochondria
   3. nucleus
   4. all these

      BIOLOGY: NUTRITION
      

      Overview
      
      
   5. Nutrition is the supply to cells and organisms, of the materials necessary to support life
   6. Many common health problems can be prevented by a healthy diet
   7. A poor diet can have injurious impact on health, leading to problems such as scurvy, beriberi and kwashiorkor
   8. A healthy diet can also significantly prevent and mitigate systemic diseases like cardiovascular disease, diabetes and osteoporosis
   9. Eating a wide variety of fresh, unprocessed food has proven favourable compared to monotonous diets of processed food
   10. Consumption of whole plant foods slows digestion, allows better absorption and a more favourable balance of nutrients
       
   Nutrients
   
   
6. There are six major classes of nutrients: carbohydrates, fats, minerals, proteins, vitamins and water
   
7. 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
     
8. Most foods contain a mixture of nutrients
9. 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

1. BIOLOGY: VACCINES
   

   Overview
   
   
2. A vaccine is a biological preparation that improves immunity to a particular disease
3. Vaccines were first used by Edward Jenner (England) in the 1770s to inoculate against small pox using the cow pox microbe
4. Vaccines have resulted in the eradication of small pox, one of the most contagious and deadly diseases known to man
5. 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
   
6. A vaccine is usually made from a weakened or dead form of the microbe that it is intended to fight
   
7. It stimulates the body’s immune system to recognise the microbe as foreign, and destroy it and remember it
8. When the same microbe re-appears later, the immune system easily recognises and destroys it
9. 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

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