The number of polypeptide chains present in a molecule of haemoglobin is/are

Options

A. 1
B. 3
C. 4
D. 2

Answer

To determine the number of polypeptide chains present in a molecule of hemoglobin, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Hemoglobin**: Hemoglobin is a globular protein found in red blood cells, primarily responsible for transporting oxygen from the lungs to the rest of the body and facilitating the return of carbon dioxide from the body back to the lungs.

2. **Structure of Hemoglobin**: Hemoglobin is composed of multiple polypeptide chains. Specifically, it consists of four polypeptide chains.

3. **Types of Chains**: Among these four chains, there are two types:
- **Alpha Chains**: There are two alpha chains in hemoglobin.
- **Beta Chains**: There are also two beta chains in hemoglobin.

4. **Amino Acids in Each Chain**: Each type of chain is made up of a specific number of amino acids:
- Each alpha chain consists of 141 amino acids.
- Each beta chain consists of 146 amino acids.

5. **Heme Groups**: Each polypeptide chain is associated with a heme group, which is crucial for oxygen binding. Since there are four polypeptide chains, there are also four heme groups in a hemoglobin molecule.

6. **Conclusion**: Therefore, the total number of polypeptide chains in a molecule of hemoglobin is four.

### Final Answer:
The number of polypeptide chains present in a molecule of hemoglobin is **4**.

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