Fetal hemoglobin differs from adult hemoglobin in that it is able to bind oxygen with greater affinity, allowing the fetus to obtain oxygen from the mother's bloodstream. This greater affinity is due to a single amino acid difference.
What accounts for this increase in affinity
A. The different amino acid causes the protein subunits to dissociate and prevents cooperative binding
B. The different amino acid favors the R state of the protein due to fewer positive charges on the protein subunit
C. The different amino acid favors the binding of Fe3+ to the heme groups over Fe2+
D. The different amino acid causes the deoxygenated hemoglobin to aggregate