Which of the following gases forms the most stable compound with haemoglobin as erythrocytes?

Options

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

Explanation

To determine which gas forms the most stable compound with hemoglobin in erythrocytes, we need to analyze the binding affinities of various gases with hemoglobin. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Understand the Role of Hemoglobin
Hemoglobin is a respiratory pigment found in red blood cells (erythrocytes) that plays a crucial role in transporting gases, primarily oxygen and carbon dioxide, throughout the body.

**Hint:** Recall that hemoglobin's primary function is to transport gases.

### Step 2: Identify the Gases Involved
The gases typically involved in the respiratory process are oxygen (O2), carbon dioxide (CO2), carbon monoxide (CO), and nitrogen (N2).

**Hint:** Think about common gases that are exchanged during respiration.

### Step 3: Analyze the Binding Affinity
- **Oxygen (O2)**: Hemoglobin binds reversibly with oxygen to transport it to body tissues.
- **Carbon Dioxide (CO2)**: Hemoglobin also binds to carbon dioxide, but with a lower affinity than oxygen.
- **Carbon Monoxide (CO)**: This gas has a significantly higher affinity for hemoglobin than oxygen, meaning it binds more strongly and can displace oxygen.
- **Nitrogen (N2)**: Hemoglobin does not have a significant role in transporting nitrogen.

**Hint:** Consider which gas binds most tightly and stably to hemoglobin.

### Step 4: Determine the Most Stable Compound
Among the gases, carbon monoxide forms the most stable compound with hemoglobin due to its high binding affinity. This can lead to carbon monoxide poisoning, as it prevents oxygen from binding effectively.

**Hint:** Think about the implications of high binding affinity in terms of stability and potential health risks.

### Conclusion
The gas that forms the most stable compound with hemoglobin in erythrocytes is **carbon monoxide (CO)**.

**Final Answer:** Carbon monoxide (CO) forms the most stable compound with hemoglobin.