Question

1. What is the role of hemoglobin in CO₂ transport?
2. What is the role of bisphosphoglycerate (BPG) in hemoglobin’s oxygen affinity?
3. Describe the process of high-altitude adaptation
4. Fetal hemoglobin has low BPG affinity. What does this mean? Why is this relevant?

Answer 1

1) About 10 percent of the carbon dioxide is transported through haemoglobin. When carbon dioxide binds to hemoglobin carbaminohemoglobin is formed. Binding of carbon dioxide to hemoglobin is reversible. Therefore, when it reaches the lungs, the carbon dioxide can freely dissociate from the hemoglobin and be expelled from the body.

2) Bisphosphoglycerate is mostly found in human red blood cells, or erythrocytes. It has a less oxygen binding affinity to oxygenated hemoglobin than it does to deoxygenated hemoglobin. It also acts to stabilize the oxygen affinity of the hemoglobin in the tense state, since the oxygen affinity is low.

3) Fetal haemoglobin exhibits a low affinity for BPG resulting in a high affinity for oxygen. The increased oxygen binding affinity is due to HbF having two α/γ dimer as opposed to the two α/β dimers of HbA. The positive histidine residues of HbA β-subunits that are essential for forming the 2,3-BPG binding pocket are replaced by serine residues in HbF γ-subunits so it has low BPG affinity.