Write short notes on Immunoglobulins.

Explanation

Whenever pathogen enters our body, the B-lymphocytes produce an army of proteins called antibodies to fight with them. They are highly specialised for binding with specific antigens. The part of an antibody that recognises an antigen is called the paratope antigen binding site.
Based on their mobility, antibodies are of two types.
1. Circulating or free antibodies: These are present in the body fluids like serum, lymph etc.
2. Membrane bound antibodies: These are present on the surface of the mature B-cells as well as the memory cells.
Structure: Immunoglobulin is a .Y. shaped molecule with four polypeptide chains of which two are long identical heavy chains (H) and two are small, identical light chains (L). These two chains are linked by disulfide bonds. One end of the antibody molecule is called Fab end (Fragment antigen binding) and the other end is called Fc end (Fragment-Crystaline). Based on the structure, the antibodies are of five types namely Ig G, Ig A, Ig M, Ig D and Ig E.