What is not part of the structure of an antibody?

Antibodies are blood proteins produced to combine with and combat specific antigens and foreign substances such as bacteria and viruses.

An antibody which is also known as immunoglobulin is a Y-shaped structure that normally consists of 4 polypeptides which are 2 heavy chains and 2 light chains. This is the structure that makes it possible for antibodies to carry out their double functions which are - Antigen binding and Biological activity mediation.

Each role is executed by different parts of the antibody. That is, the fragment crystallizable region known as the fc region and the fragment antigen binding known as fab fragment.

The fab fragment is an area on the antibody that joins to antigens. It normally consists of one variable and one static domain of each of the light chain as well as the heavy one.

The fragment crystallizable region is the tail area of an antibody that combines with surface receptors and proteins of the complement system. This normally enables the antibodies to activate the immune system