Question

Arrange the affinity of hemoglobin (Hb) towards \( \mathrm{CO} \), \( \mathrm{CO_2} \), and \( \mathrm{O_2} \) in increasing order.

• A. \( \mathrm{O_2}>\mathrm{CO_2}>\mathrm{CO} \)
• B. \( \mathrm{CO_2}>\mathrm{O_2}>\mathrm{CO} \)
• C. \( \mathrm{O_2}>\mathrm{CO}>\mathrm{CO_2} \)
• D. \( \mathrm{CO}>\mathrm{CO_2}>\mathrm{O_2} \)

Hint:

Remember that carbon monoxide (\( \mathrm{CO} \)) forms a stable complex with hemoglobin, leading to carbon monoxide poisoning. Oxygen therapy is used to displace \( \mathrm{CO} \) from hemoglobin.

Answer 1

The Correct Option is D

The affinity of hemoglobin (Hb) for different gases is determined by their chemical interactions with the heme group. Here is the order of affinity: Carbon monoxide (\( \mathrm{CO} \)): Hemoglobin has the highest affinity for \( \mathrm{CO} \), which is about 200-300 times greater than its affinity for \( \mathrm{O_2} \). This strong binding significantly reduces oxygen transport when \( \mathrm{CO} \) is present. Carbon dioxide (\( \mathrm{CO_2} \)): Hemoglobin binds \( \mathrm{CO_2} \) to form carbaminohemoglobin, but the affinity is much lower compared to \( \mathrm{CO} \). Oxygen (\( \mathrm{O_2} \)): Hemoglobin has a lower affinity for \( \mathrm{O_2} \) compared to \( \mathrm{CO_2} \) and \( \mathrm{CO} \). Thus, the order of affinity is: \[ \mathrm{CO}>\mathrm{CO_2}>\mathrm{O_2}. \]