Which statement is incorrect about the Fc region of an immunoglobulin?

• A. The Fc region can activate the complement system.
• B. The Fc region is responsible for binding to cell surface receptors.
• C. The Fc region determines the class of the immunoglobulin.
• D. The Fc region is involved in antigen binding.

Answer: (D)

Verified step by step guidance

1. Understand the structure of an immunoglobulin: Immunoglobulins, or antibodies, are Y-shaped molecules composed of two main regions: the Fab region and the Fc region.
2. Identify the function of the Fab region: The Fab (Fragment antigen-binding) region is responsible for binding to antigens. It is the variable part of the antibody that recognizes and binds to specific antigens.
3. Identify the function of the Fc region: The Fc (Fragment crystallizable) region is the constant part of the antibody that interacts with cell surface receptors and the complement system. It does not bind to antigens.
4. Evaluate the given statements: Compare each statement with the known functions of the Fc region. The Fc region can activate the complement system, bind to cell surface receptors, and determine the class of the immunoglobulin.
5. Determine the incorrect statement: The statement 'The Fc region is involved in antigen binding' is incorrect because antigen binding is the function of the Fab region, not the Fc region.