Antigenic determinant site binds to which portion of an antibody molecules?

Options

A. A.Light chanis
B. B.heavy chains
C. C.Intermediate chains
D. D.Both 1 and 2

Answer

**Step-by-Step Solution:**

1. **Understanding Antibodies**: Antibodies are proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses. They consist of two types of chains: heavy chains and light chains.

2. **Identifying Antigens**: Antigens are substances that trigger an immune response. They have specific regions known as epitopes, which are recognized by antibodies.

3. **Antigen Binding Site**: The region on the antibody where the epitope of the antigen binds is known as the antigen binding site. This site is crucial for the immune response.

4. **Composition of the Antigen Binding Site**: The antigen binding site is formed by both the light chains and heavy chains of the antibody. This means that both types of chains contribute to the structure that interacts with the antigen.

5. **Conclusion**: Therefore, the antigenic determinant site binds to both the light chains and heavy chains of the antibody molecule. The correct answer is option D: both 1 and 2.

---