Question

Fetal hemoglobin binds 2,3-BPG with a lower affinity than adult hemoglobin. Briefly explain your answers.

a) Will fetal hemoglobin have more or less 2,3-BPG bound than the mother's hemoglobin?

b) Will the O2 saturation curve for fetal hemoglobin be shifted to the right or to the left from the curve for adult hemoglobin?

c) Will fetal hemoglobin have a higher or lower affinity for O2 than the mother's hemoglobin?

Answer 1

(a). Fetal hemoglobin have less 2,3-BPG bound than the mother's hemoglobin because fetal hemoglobin has more affinity to oxygen than adult hemoglobin. It binds with greater affinity to deoxygenated hemoglobin as compared to oxygenated hemoglobin due to difference in their sizes: 2,3-BPG (9 angstroms) fits in the deoxygenated hemoglobin (11 angstroms), but not in the oxygenated (5 angstroms).

(b). Since fetal hemoglobin has a greater affinity for oxygen, the O2 saturation curve for fetal hemoglobin is shifted to the left from the curve for adult hemoglobin.

(c). Fetal hemoglobin has a greater affinity for oxygen than the mother's hemoglobin.