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