Excessive release of the pollutant carbon monoxide (CO) into the air may produce a condition in which oxygen supply in the human body decreases. What causes this condition ?
A
When inhaled into the human body, CO is converted into CO2
B
The inhaled CO has much higher affinity for haemoglobin as com- pared to oxygen
C
The inhaled CO destroys the chemical structure of haemoglobin
D
The inhaled CO adversely affects the respiratory centre in the brain
Correct Answer: Option B
Explanation
1. The question describes a condition caused by excessive carbon monoxide (CO) release into the air, where oxygen supply in the human body decreases, and asks for the cause.
2. Carbon monoxide is a poisonous gas produced by incomplete combustion.
3. When inhaled, CO enters the bloodstream and binds to haemoglobin, the molecule in red blood cells responsible for carrying oxygen.
4. Statement (B): The inhaled CO has much higher affinity for haemoglobin as compared to oxygen. CO binds to haemoglobin about 200-250 times more strongly than oxygen does. This forms carboxyhemoglobin (COHb).
5. Because CO binds so tightly, it effectively blocks haemoglobin from picking up and transporting oxygen from the lungs to the body tissues, leading to oxygen deprivation (hypoxia). This correctly explains the condition.
6. Statement (A) is incorrect; CO is not readily converted to CO2 in the body.
7. Statement (C) is incorrect; CO binds to haemoglobin but doesn't destroy its chemical structure.
8. Statement (D) is incorrect; while severe CO poisoning affects the brain, the primary mechanism of reduced oxygen supply is competitive binding with haemoglobin.