Question

The antigen binding site of an antibody is present

• A. at the constant region
• B. at the C-terminal
• C. at the variable region
• D. between the constant and the variable region

Hint:

Remember: Antigen specificity of antibodies is due to variation in the variable (V) regions, not the constant (C) regions.

Answer 1

The Correct Option is C

Step 1: Understanding antibody structure.
Antibodies (immunoglobulins) consist of constant and variable regions. The variable regions of both heavy and light chains form the antigen-binding site. These regions differ from one antibody to another and determine antigen specificity.
Step 2: Analyzing the options.
(A) Constant region: This part is responsible for effector functions, not binding.
(B) C-terminal: This is part of the constant region; not involved in antigen recognition.
(C) Variable region: Correct — antigen binding occurs here.
(D) Between constant and variable region: This area is not involved in specific antigen binding.
Step 3: Conclusion.
The antigen-binding site is entirely located in the variable regions of the heavy and light chains.