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Thursday, 16 March 2017

Bio molecule - III

1. Proteins: These are micro molecules made up of amino acids joined via a peptide link ( ‐(‐CONH‐)‐ is the peptide linkage). These are required for growth and development of the body.

2. Amino Acids: These contain an amino (‐NH2) and an acidic (‐COOH) group and are therefore amphoteric in nature. In solution they exist in the form of zwitter ion.

3. Classification

4. Structure And Shape of Protein
Primary Strutcure :
The specific sequence of amino acids in the polypeptide chain. Change in amino acids sequence changes the protein. They have covalent bonds.

Secondary Structure :

It isthe shape in which the long polypeptide chain can exist. It is of two types : α‐ helix and β‐ pleated. These structures arise due to regular folding of the backbone of the polypeptide chain due to H‐bonding between the C = o and –NH‐ groups of the peptide bond

Tertiary Structure :
Represents overall folding of the polypeptide chain. It gives rise to the fibrous or globular molecular shapes. Forces stabilizing the 2oand 3ostructures are hydrogen bonds, disulphide linkages, van der waal’s and electrostatic forces of attraction.

Quaternary Structure :
Protein can be composed of two or more polypeptide chains called sub units. The spatial arrangement of these sub units with respect to each other quaternary structure of the protein.

5. Denaturaion of Protein: The protein in native state, when subjected to a physical change like temperature, pH etc undergoes uncoiling and looses it’s biological activity. The 2oand 3ostructures are destroyed, only 1ostructure is retained.

Renaturation of Protein:
Some proteins regain their biological activity by reversible process it is called Renaturation of Proteins. In such a cases, when temperature in pH of a denatured proteins is brought back to conditions in which the native protein is stable, secondary and tertiary structures of proteins are restored to which leads to recovery of biological activity.

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