Which of the following binds with haemoglobin irreversibly?

Options

A. Carbon dioxide
B. Oxygen
C. Carbon monoxide
D. Nitrogen

Answer

To solve the question "Which of the following binds with haemoglobin irreversibly?", we will analyze the options provided and understand the binding characteristics of each substance with hemoglobin.

### Step-by-Step Solution:

1. **Understanding Hemoglobin**:
- Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen throughout the body. It has four heme groups that can bind to oxygen molecules.

2. **Analyzing the Options**:
- **Option 1: Carbon Dioxide (CO2)**:
- Carbon dioxide binds to hemoglobin but does so reversibly. It can be released from hemoglobin when needed.
- **Option 2: Oxygen (O2)**:
- Oxygen binds reversibly to hemoglobin. This means it can attach and detach as required by the body's tissues.
- **Option 3: Carbon Monoxide (CO)**:
- Carbon monoxide binds to hemoglobin irreversibly. It attaches to the same site as oxygen but does so with a much stronger affinity, making it difficult for oxygen to bind.
- **Option 4: Nitrogen (N2)**:
- Nitrogen does not significantly bind to hemoglobin in a physiological context.

3. **Identifying the Irreversible Binding**:
- From the analysis, carbon monoxide (CO) is the only substance that binds irreversibly to hemoglobin. This means once it binds, it does not easily detach, which can lead to harmful effects in the body.

4. **Conclusion**:
- The correct answer to the question is **Carbon Monoxide (CO)**, which binds irreversibly to hemoglobin.

### Final Answer:
**Carbon Monoxide (CO)** binds with haemoglobin irreversibly.

---