Antigen binding site in an antibody is found between:

Options

A. Two light chains
B. Two heavy chains
C. One heavy and one light chain
D. Both B and C depending upon nature of antigen

Answer

To answer the question regarding where the antigen binding site in an antibody is found, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Antibodies**: Antibodies, also known as immunoglobulins, are Y-shaped proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses.

2. **Structure of Antibodies**: Each antibody consists of four polypeptide chains: two heavy chains and two light chains. The arrangement of these chains forms a Y-shaped structure.

3. **Identifying the Antigen Binding Site**: The antigen binding site, also known as the paratope, is the specific region on the antibody that recognizes and binds to an antigen.

4. **Location of the Antigen Binding Site**: The paratope is located at the tips of the Y-shaped structure of the antibody. Each arm of the Y contains one light chain and one heavy chain.

5. **Analyzing the Options**:
- **Option A**: Two light chains - Incorrect, as this does not form the antigen binding site.
- **Option B**: Two heavy chains - Incorrect, as this does not form the antigen binding site.
- **Option C**: One heavy and one light chain - Correct, as this combination forms the antigen binding site.
- **Option D**: Both B and C - Incorrect, since only option C is correct.

6. **Conclusion**: The antigen binding site is found between one heavy chain and one light chain. Therefore, the correct answer is option C.

### Final Answer:
The antigen binding site in an antibody is found between **one heavy chain and one light chain**.

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