Vitamins, Harmones and Hemoglobin
Which one of the following statements concerning the hemoglobins is correct?
|A||Fetal blood has a higher affinity for oxygen than does adult blood because Hb F has a decreased affinity for 2,3-BPG.|
|B||Purified Hb F (stripped of 2,3-BPG) has a higher affinity for oxygen than does purified Hb A.|
|C||The chain composition of Hb F is α2δ2.|
|D||Hb A1c differs from Hb A by a single, genetically determined amino acid substitution.|
a. Because 2,3-BPG reduces the affinity of hemoglobin for oxygen, the weaker interaction between 2,3-BPG and Hb F results in a higher oxygen affinity for Hb F relative to Hb A. In contrast, if both Hb A and Hb F are stripped of 2,3-BPG, they have a similar affinity for oxygen. Hb F consists of α2γ2.
b. Hb A1c is a glycosylated form of Hb A, formed nonenzymically in red cells. Hb A2 is a minor component of normal adult hemoglobin, first appearing about twelve weeks after birth.