Describe the structure of an antibody.
Structure of antibody
Antibodies are glycoproteins that are highly specific to specific antigens.
Antibodies are also known as Immunoglobulins (Igs), produced in response to antigenic stimulation.
Antibodies are produced by plasma cells which in turn are formed by B–lymphocytes.
The mature plasma cells produce antibodies at an extremely rapid rate i.e. about 2000 molecules per second.
Structure of antibody:
- The antibody is a ‘Y’ shaped molecule.
- Each immunoglobulin molecule is made up of four polypeptide chains.
- There are two heavy or H-chains and two light or L-chains.
- The four polypeptide chains are held together by disulfide bonds (-s s-) to form a ‘Y’ shaped structure.
- The region holding together the arms and stem of the antibody is termed the hinge.
- Each chain of the antibody includes two distinct regions, the variable region, and the constant region.
- Variable regions constitute the antigen-binding site (paratope).
- This part of the antibody recognizes and binds to the specific antigen to form an antigen-antibody complex.
- Since most antibodies carry two antigen-binding sites, they are said to be bivalent.