Which type of hemoglobin has higher affinity for oxygen, facilitating transfer from mother to fetus?

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Multiple Choice

Which type of hemoglobin has higher affinity for oxygen, facilitating transfer from mother to fetus?

The key idea is why fetal blood grabs oxygen more strongly than adult blood. Fetal hemoglobin has a higher affinity for oxygen, thanks to its gamma chains and its reduced interaction with the molecule that normally lowers hemoglobin’s O2 affinity (2,3-BPG). This makes the oxygen-hemoglobin dissociation curve shift to the left for fetal Hb, so at the same placental oxygen levels, fetal Hb binds O2 more readily and releases it less readily to fetal tissues. In the placenta, this allows oxygen to move from maternal blood into the fetal blood efficiently. After birth, HbF is gradually replaced by HbA, which has lower O2 affinity and is better suited for delivering O2 to tissues throughout the body. The other options don’t fit because adult HbA binds O2 less tightly than HbF, methemoglobin cannot effectively bind O2, and HbC is a variant that does not provide the same high fetal O2 affinity.

The key idea is why fetal blood grabs oxygen more strongly than adult blood. Fetal hemoglobin has a higher affinity for oxygen, thanks to its gamma chains and its reduced interaction with the molecule that normally lowers hemoglobin’s O2 affinity (2,3-BPG). This makes the oxygen-hemoglobin dissociation curve shift to the left for fetal Hb, so at the same placental oxygen levels, fetal Hb binds O2 more readily and releases it less readily to fetal tissues. In the placenta, this allows oxygen to move from maternal blood into the fetal blood efficiently.

After birth, HbF is gradually replaced by HbA, which has lower O2 affinity and is better suited for delivering O2 to tissues throughout the body. The other options don’t fit because adult HbA binds O2 less tightly than HbF, methemoglobin cannot effectively bind O2, and HbC is a variant that does not provide the same high fetal O2 affinity.

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