Question

Which one of the following gases converts haemoglobin into carboxy haemoglobin ?

• A. CO
• B. O₂
• C. NO
• D. CO₂

Answer 1

The Correct Option is A

The gas that converts haemoglobin into carboxyhaemoglobin is carbon monoxide (CO).

Explanation: 

• (A) CO (Carbon monoxide): Correct. Carbon monoxide binds strongly and irreversibly with haemoglobin, forming carboxyhaemoglobin, reducing oxygen-carrying capacity.
• (B) O₂ (Oxygen): Incorrect. Oxygen binds with haemoglobin to form oxyhaemoglobin, not carboxyhaemoglobin.
• (C) NO (Nitric oxide): Incorrect. Nitric oxide can bind to haemoglobin, forming nitrosyl haemoglobin, but it doesn't form carboxyhaemoglobin.
• (D) CO₂ (Carbon dioxide): Incorrect. Carbon dioxide binds reversibly with haemoglobin to form carbaminohaemoglobin, not carboxyhaemoglobin.

Conclusion:

The correct answer is Option (A): CO (Carbon monoxide).

Answer 2

Carbon monoxide (CO) is the gas that binds with hemoglobin to form carboxyhemoglobin. It has a much higher affinity for hemoglobin than oxygen, displacing oxygen and preventing its normal function in transporting oxygen to tissues. This results in the formation of carboxyhemoglobin, which is a stable complex and reduces the oxygen-carrying capacity of blood.

Other gases like O₂, NO, and CO₂ do not form carboxyhemoglobin. O₂ binds to hemoglobin to form oxyhemoglobin, while CO₂ binds to hemoglobin to form carbaminohemoglobin, but not carboxyhemoglobin.

So, the correct answer is (A): CO