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Hemoglobin: Oxygen Binding


Hemoglobin is a tetrameric protein with one ${ O }_{ 2 }$-binding heme prosthetic group associated with each subunit. When ${ O }_{ 2 }$ binds to one of the hemes, it causes a conformational shift in the protein increasing the ${ O }_{ 2 }$ binding affinity at the other three hemes.

Oxygen binding to hemoglobin is also regulated by the allosteric effector, 2,3-bisphosphoglycerate (BPG), which is typically found in high concentrations in the blood. Hemoglobin binds 1 BPG per tetramer and BPG in turn reduces the affinity of hemoglobin for ${ O }_{ 2 }$.

Understanding the relationships between hemoglobin, ${ O }_{ 2 }$ binding and BPG, which of the following scenarios is NOT supported?


BPG levels typically increase when a person living at sea level in San Francisco visits Denver, Colorado.


Fetal hemoglobin typically has a much higher affinity for BPG than maternal hemoglobin.


A person suffering from chronic obstructive pulmonary disease (COPD) would be aided by increased synthesis of intracellular BPG.


Increased levels of intracellular BPG in pregnant women would aid the fetus.