A pregnant woman is able to transfer oxygen to her fetus because fetal hemoglobin has a greater affinity for oxygen than does adult hemoglobin. Why is the affinity of fetal hemoglobin for oxygen higher: (A) The oxygen-binding curve of fetal hemoglobin is shifted to the right., (B) Fetal hemoglobin binds 2,3-BPG with fewer ionic bonds than the adult form., (C) There is less 2,3-BPG in the fetal circulation as compared to maternal circulation, (D) The tense form of hemoglobin is more prevalent in the circulation of the fetus
Answer is B. In adult hemoglobin 2,3-BPG binds to ionized residues in the interface between the two b-chains, thus decreasing the oxygen affinity. The g-chains of fetal hemoglobin have fewer ionized residues in the corresponding interface and bind 2,3-BPG with less affinity, which allows for a greater binding affinity for oxygen. Ref:- Lippincott textbook of Biochemistry