Question

The allosteric effector molecule 2,3-BPG facilitates transfer of oxygen between maternal and fetal blood in the placenta. Which of the following correctly describes the role of BPG in this process?
a. Fetal hemoglobin binds oxygen better than maternal hemoglobin because BPG is unable to cross the placenta into fetal blood, causing more fetal hemoglobin to be in the R state.
b. Fetal hemoglobin binds oxygen better than maternal hemoglobin because BPG is present at similar levels in fetal and maternal blood, but it binds poorly to fetal hemoglobin, causing more fetal hemoglobin to be in the R state.
c. Fetal hemoglobin binds oxygen better than maternal hemoglobin because BPG is present at similar levels in fetal and maternal blood, but it binds poorly to fetal hemoglobin, causing more fetal hemoglobin to be in the T state.
d. Fetal hemoglobin releases oxygen better than maternal hemoglobin because BPG is present at similar levels in fetal and maternal blood, but it binds more effectively to fetal hemoglobin causing more fetal hemoglobin to be in the T state.

Answer 1

Answer:

b. Fetal hemoglobin binds oxygen better than maternal hemoglobin because BPG is present at similar levels in fetal and maternal blood, but it binds poorly to fetal hemoglobin, causing more fetal hemoglobin to be in the R state.

Explanation:

BPG is a chemical compound which is found in red blood cells. It is known for decreasing the affinity of hemoglobin with oxygen and thus helps in unloading oxygen from hemoglobin.

Owing to the structural difference, fetal hemoglobin binds to BPG with less affinity as compared to maternal hemoglobin thus it shifts the oxyhemoglobin curve to the left i.e. causes fetal hemoglobin to be in the R state. Due to this, fetal hemoglobin can carry up to 30% more oxygen as compared to maternal hemoglobin. As a result of this, oxygen is readily transferred to fetal blood when maternal blood enters placenta which restricts hypoxia in fetus.