Explain the structure of antibodies.

Explanation

1. It is a Y-shaped protein molecule whose surface has a shape complementary to the determinant group of the antigen.
2. Each antibody molecule is made up of 4 polypeptide chains.
3. Out of four polypeptide chains, 2 of them are identical short stands called light chains with low molecular weight and other two are identical long strands called heavy chains with high molecular weight. Long chain contains around 400 amino acids whereas the short chain contains 200 amino acids.
4. These four chains are held together by disulphide bonds forming a Y-shaped molecule.
5. Each chain has a constant region (C) and a variable region (V).
6. The variable regions are present at the tip of each arm of the Y-molecule. They form an antigen binding site. The rest of the arm forms the constant region.