Image taken from Wikipedia
The reason why fetal hemoglobin has a greater affinity for oxygen is due to the lack of its interaction with a molecule called 2,3-bisphosphoglycerate. This substance decreases the affinity of adult hemoglobin for oxygen. It is
also present in fetal red blood cells, but does not interact with fetal
hemoglobin.
Just to summarize the difference between fetal and adult hemoglobin as asked in class, fetal hemoglobin has 2 gamma polypeptide chains instead of 2 beta chains like adult hemoglobin. So there IS a difference in structure which contributes to the higher affinity to oxygen in fetal hemoglobin. The gamma subunit has fewer positive charges than the adult
hemoglobin beta subunit. This means that 2,3-bisphosphoglycerate is less electrostatically
bound to fetal hemoglobin as compared to adult hemoglobin. This means
that 2,3-bisphosphoglycerate is less effective in lowering the oxygen affinity of the
fetal hemoglobin.
In looking for more information on fetal hemoglobin, I stumbled upon a
paper available on PubMed which I trust will be useful for A Level
Biology students as it links fetal hemoglobin with sickle cell anemia,
both of which are covered in the syllabus. Refer to the link below:
And
now there's the possibility of reversing sickle cell anemia by turning
on the production of fetal hemoglobin in adults. Read the article at the
link below:
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