5. 2, 3-bisphosphoglycerate (BPG) is not only important for our adaptation to li

Question

5. 2, 3-bisphosphoglycerate (BPG) is not only important for our adaptation to living at high altitudes, but also critical for oxygen transport at sea level. Who would have a higher level of BPG: a person living at sea level or one at 4,500 m above sea level? Explain. (a) (5 marks) In order for the structural transition from T to R to take place, the bonds between hemoglobin and 2,3-BPG must be broken and 2,3-BPG must be expelled. (b) What is the effect of BPG on fetal hemoglobin binding to oxygen? (3 marks)

Explanation / Answer

a) 2,3 Biphosphoglycerate affects the oxygen carrying capacity apart from temperature and pressure. It is simply called as 2,3-BPG which is three carbon intermediate of the glycolysis step. They enter the red blood cells and bond to hemoglobin molecules due to allosteric structure which have more compatibility for the hemoglobin than the oxygen this binding will leads to disassociation of oxygen molecules and this oxygen molecules can be transferred to other tissues by this the oxygen is transported to other parts of body organs. Person living in higher altitudes above sea levels high levels of 2,3-BPG molecules as high altitude area have low oxygen levels and to transport oxygen molecule to tissues of body more amount of 2,3-BPG molecule are higher in concentration while the person in the are of lower sea level.

b) Fetal hemoglobin has a greater affinity for the oxygen because of the less interaction between fetal hemoglobin and 2,3-phosphoglycerate.As most of mother blood oxygen is transferred to fetus less amount of 2,3-BPG interaction takes place with fetal hemoglobin and much of interaction is with oxygenated blood of mother. Moreover fetal hemoglobin contains a different amino acid serine which is negatively charged and doesn’t react with the 2,3-BPG compared to adult hemoglobin which has positively charged amino histidine which interacts with 2,3-BPG.

c) Carbon dioxide and carbon monoxide binds with oxygen in the hemoglobin forming stable carboxyhemoglobin molecule. This reduces the oxygen carrying capacity of blood. The heme group of hemoglobin has high affinity for oxygen atoms but in the presence of carbon dioxide and carbon monoxide the heme group loses oxygen and forms carboy hemoglobin which inhibits oxygen movement.2,3-BPG molecules displaces the oxygen molecule and releases while the carbon dioxide and carbon monoxide forms a stable compound carboxyhemoglobin.

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