In the structure of an antibody, which regions are responsible for binding to antigens?

• A. The variable regions of the light and heavy chains
• B. The Fc region
• C. The hinge region
• D. The constant region of the heavy chain

Answer: (A)

Verified step by step guidance

1. Understand the basic structure of an antibody, which consists of two heavy chains and two light chains forming a Y-shaped molecule.
2. Recognize that each chain has both constant and variable regions; the variable regions differ between antibodies and are responsible for antigen specificity.
3. Identify that the antigen-binding sites are located at the tips of the Y, where the variable regions of both the heavy and light chains come together.
4. Note that the constant regions, including the Fc region and hinge region, are involved in effector functions and flexibility but do not bind antigens.
5. Conclude that the regions responsible for binding to antigens are the variable regions of the light and heavy chains.