Overview: Biomolecules

The complex lifeless organic substances which form the basis of life and are responsible for the growth and maintenance of living systems are called biomolecules.

The sum total of all chemical reactions occurring in a living organism is called metabolism.

The sequence of enzyme-catalysed reactions by which food is converted into body parts is called a metabolic pathway.

Polyhydroxy aldehydes or polyhydroxy ketones, or substances which on hydrolysis yield such compounds, are called carbohydrates.

Carbohydrates which cannot be hydrolysed to give simpler carbohydrates are called monosaccharides.

Carbohydrates which on hydrolysis give a definite number (2–10) of monosaccharide units are called oligosaccharides.

Carbohydrates which on hydrolysis give two monosaccharide units are called disaccharides.

Carbohydrates which on hydrolysis give three monosaccharide units are called trisaccharides.

Carbohydrates which on hydrolysis give four monosaccharide units are called tetrasaccharides.

Carbohydrates which on hydrolysis give a large number of monosaccharide units are called polysaccharides.

Carbohydrates capable of reducing Tollens’ reagent and Fehling’s solution are called reducing sugars.

Monosaccharides containing an aldehyde (–CHO) group are called aldoses.

Monosaccharides containing a keto (>C=O) group are called ketoses.

Monosaccharides containing seven carbon atoms are called heptoses.

Two stereoisomers which are mirror images of each other and are non-superimposable are called enantiomers.

The spontaneous change in optical rotation of an optically active compound in aqueous solution until equilibrium is reached is called mutarotation.

A pair of stereoisomers which differ in configuration around the anomeric carbon atom are called anomers.

The linkage formed between two monosaccharide units through an oxygen atom by condensation is called a glycosidic linkage.

The principal storage polysaccharide of plants composed of α-glucose units is called starch.

The linear water-soluble component of starch composed of α-1,4-glycosidic linked glucose units is called amylose.

The branched water-insoluble component of starch composed of α-1,4 and α-1,6-glycosidic linked glucose units is called amylopectin.

The structural polysaccharide of plants composed of β-1,4-glycosidic linked glucose units is called cellulose.

The storage polysaccharide of animals found in liver and muscles is called glycogen.

The internal salt formed due to transfer of a proton from —COOH group to —NH₂ group in aqueous solution is called a zwitter ion.

The pH at which an amino acid exists as a neutral dipolar ion and does not migrate in an electric field is called the isoelectric point.

The compounds obtained by condensation of two or more α-amino acids are called peptides.

The peptide formed by condensation of many α-amino acids is called a polypeptide.

The —CO—NH— bond formed by condensation of two amino acid molecules is called a peptide bond or peptide linkage.

The long polymers of amino acids linked together by peptide bonds and having high molecular mass are called proteins.

Globular proteins which act as biological catalysts in living systems and are produced by living cells are called enzymes.

The protein part of an enzyme without its cofactor is called an apoenzyme.

The complete catalytically active enzyme consisting of apoenzyme and cofactor is called a holoenzyme.

Chemical substances secreted by ductless glands which regulate development and control activities of the body are called hormones.

Biomolecules present in the nuclei of living cells which are responsible for storage and transmission of genetic information are called nucleic acids.

The monomer unit of a nucleic acid is called a nucleotide.

The base-sugar unit present in a nucleic acid chain is called a nucleoside.

The linkage formed between nucleotides through phosphate group between 5′ and 3′ carbon atoms is called a phosphodiester linkage.

The rule stating that in DNA the amount of adenine equals thymine and the amount of cytosine equals guanine is called Chargaff’s rule.

The sequence of DNA that codes for a specific protein or polypeptide is called a gene.

A chemical change in a DNA molecule which leads to the synthesis of proteins with a different amino acid sequence is called a mutation.

The defective form of a gene resulting from mutation and capable of causing genetic disorders is called a mutant gene.

1. Carbohydrates are the main source of energy for living organisms and act as body fuels.
2. Carbohydrates are stored as reserve food in plants as starch and in animals as glycogen.
3. It provide structural support in plants by forming the cell wall (cellulose).
4. Glucose formed from carbohydrates is oxidised in the body to release energy required for life processes.

• The property by which an enzyme acts only on a specific substrate and catalyses only a particular type of reaction is called specificity of enzymes.
• The ability of enzymes to increase the rate of a reaction by many times compared to uncatalysed reactions is called catalytic efficiency of enzymes.
• The property by which a very small amount of enzyme is sufficient to catalyse a large amount of substrate because the enzyme is regenerated is called high catalytic power of enzymes.
• The condition at which the activity of an enzyme is maximum at a particular temperature and pH is called the optimum temperature and optimum pH of an enzyme.

1. Vitamins are biological catalysts required in very small amounts to regulate various metabolic reactions in the body.
2. Deficiency of one or more vitamins causes specific deficiency diseases, and this condition is called avitaminosis.
3. Vitamins help in growth, metabolism, immunity, maintenance of tissues, blood formation and proper functioning of organs.
4. Different vitamins have specific functions and sources, and their deficiency leads to characteristic diseases such as night blindness (Vitamin A), beriberi (Vitamin B₁), scurvy (Vitamin C) and rickets (Vitamin D).