The specificity of an antibody is due to which of the following?

• A. The Fc region of the antibody
• B. The constant region of its heavy chain
• C. The variable region of its antigen-binding site
• D. The carbohydrate side chains attached to the antibody

Answer: (C)

Verified step by step guidance

1. Understand that an antibody molecule has different regions, each with specific functions: the Fc region, the constant region of the heavy chain, the variable region, and carbohydrate side chains.
2. Recall that the Fc region is responsible for interacting with cell receptors and complement proteins, not for antigen specificity.
3. Recognize that the constant region of the heavy chain provides structural stability and mediates effector functions but does not determine antigen specificity.
4. Focus on the variable region of the antibody, which contains unique amino acid sequences that form the antigen-binding site, allowing the antibody to specifically recognize and bind to a particular antigen.
5. Note that carbohydrate side chains are involved in antibody stability and solubility but do not contribute to antigen specificity.