Question

Briefly describe the structure and function of antibody molecule.

Hint:

Picture a Y shape built from two long and two short protein chains, with variable tips that grab the antigen.

Answer 1

Step 1: Understanding the Concept:
When a foreign substance (antigen) enters the body, the immune system responds by making special protein molecules designed to recognise and bind that specific antigen. These are antibodies.

Step 2: Describe the structure.
An antibody molecule is shaped like the letter Y and is built from four polypeptide chains: two identical long chains called heavy chains, and two identical short chains called light chains, all held together by disulfide bonds.
Each chain has a constant region (which stays the same across antibodies of the same class) and a variable region (which differs and forms the antigen-binding site at the tips of the Y).

Step 3: Describe the function.
The variable regions at the two arms of the Y bind specifically to a matching antigen, like a lock fitting a key, which either neutralises the antigen directly or tags it so other immune cells can destroy it.

Final Answer:
An antibody is a Y-shaped protein of two heavy and two light chains, whose variable tips bind specifically to an antigen to neutralise or mark it for destruction.