Hemoglobin's Affinity for Oxygen When the BPG Level is High

Question

Hemoglobin's affinity for oxygen when the BPG level is high is
A) greater than hemoglobin's affinity for oxygen when the BPG level is low.
B) less than hemoglobin's affinity for oxygen when the BPG level is low.
C) equal to hemoglobin's affinity for oxygen when the BPG level is low.
D) equal to hemoglobin's affinity for oxygen when pH is low.
E) equal to hemoglobin's affinity for oxygen when pH is high.

Accepted Answer

When the level of BPG (2,3-bisphosphoglycerate) is high, hemoglobin's affinity for oxygen decreases. BPG binds to a pocket in the hemoglobin molecule and stabilizes the low-affinity state, which promotes oxygen release to tissues. Therefore, at high levels of BPG, hemoglobin has a lower affinity for oxygen. Option A is incorrect because a high level of BPG would decrease the affinity for oxygen. Option C is incorrect because the affinity is not equal when the BPG level is high versus low. Options D and E are incorrect because pH does not have a direct effect on the presence of BPG in the hemoglobin molecule.