How many oxygen molecules can a single molecule of haemoglobin transport at a time?

Options

A. One
B. Eight
C. Four
D. Five

Answer

To solve the question of how many oxygen molecules a single molecule of hemoglobin can transport at a time, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Hemoglobin Structure**:
- Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs.

**Hint**: Remember that hemoglobin is a protein with a specific structure that allows it to bind to oxygen.

2. **Identifying the Components of Hemoglobin**:
- Hemoglobin contains iron (Fe) at its core, which is crucial for oxygen binding. Each hemoglobin molecule is made up of four subunits, and each subunit contains a heme group that has an iron atom.

**Hint**: Focus on the role of the iron atom in the heme group for oxygen binding.

3. **Binding Sites for Oxygen**:
- Each of the four heme groups in hemoglobin can bind to one molecule of oxygen (O2). Therefore, a single hemoglobin molecule has four binding sites for oxygen.

**Hint**: Count the number of heme groups in hemoglobin and relate them to the oxygen binding capacity.

4. **Conclusion**:
- Since each of the four heme groups can bind to one oxygen molecule, a single molecule of hemoglobin can transport a total of four oxygen molecules at a time.

**Hint**: Summarize the findings to arrive at the final answer.

### Final Answer:
A single molecule of hemoglobin can transport **4 oxygen molecules** at a time.