How many variable segments are present in the basic structure of an antibody molecule?

Options

A. One
B. Two
C. Three
D. Four

Answer

To determine how many variable segments are present in the basic structure of an antibody molecule, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Antibodies**:
- Antibodies are Y-shaped molecules made up of four polypeptide chains: two heavy chains and two light chains.

2. **Identify the Regions of Antibodies**:
- Each antibody has two main regions: the variable region and the constant region.
- The variable region is responsible for binding to antigens.

3. **Locate the Variable Regions**:
- Each light chain has one variable region.
- Each heavy chain also has one variable region.

4. **Count the Variable Regions**:
- Since there are two light chains and two heavy chains, we can calculate the total number of variable regions:
- 1 variable region from each light chain = 2 variable regions from light chains.
- 1 variable region from each heavy chain = 2 variable regions from heavy chains.
- Therefore, the total number of variable regions = 2 (from light chains) + 2 (from heavy chains) = 4 variable regions.

5. **Conclude the Answer**:
- Thus, the total number of variable segments present in the basic structure of an antibody molecule is 4.

### Final Answer:
The number of variable segments present in the basic structure of an antibody molecule is **4**.

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