Page 143 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

Basic structure of immunoglobulins

Although different immunoglobulins can differ structurally, they all are built from

the same basic unit.

1. Heavy and light chain

All immunoglobulins have a four-chain structure as their basic unit.

• Two identical heavy chains (high molecular weight)

• Two identical light chains (low molecular weight)

2. Disulfide bonds

• join the two chains, creating a Y-shaped molecule with identical halves.

• join the two halves of the molecule. At the fork of the Y is a flexible, or “hinge,”

region.

3- D-Hinge region
• The region at which the arms of the antibody molecule form a Y is called the

hinge region because there is some flexibility in the molecule at this point.

General Microbiology & Immunology (PM 401) theoretical handbook Page 132