The hemoglobin of a human fetus.

Options

A. Has higher affinity for oxygen than that of an adult
B. Has a lower affinity for oxygen than that of an adult
C. Has same affinity for oxygen as that of an adult
D. Has two protein sub- units instead of four.

Answer

**Step-by-Step Solution:**

1. **Understanding Hemoglobin**: Hemoglobin is a protein found in red blood cells (erythrocytes) that functions as a respiratory pigment. It is crucial for the transport of oxygen from the lungs to body tissues and the removal of carbon dioxide from tissues back to the lungs.

2. **Fetal Development**: In a developing fetus, the exchange of gases and nutrients occurs through the placenta, which connects the mother and the fetus. This is essential for the fetus's survival as it relies on the mother's blood supply for oxygen and nutrients.

3. **Affinity for Oxygen**: The key difference between fetal hemoglobin (HbF) and adult hemoglobin (HbA) is the affinity for oxygen. Fetal hemoglobin has a higher affinity for oxygen compared to adult hemoglobin. This means that HbF can bind oxygen more readily than HbA, which is crucial for the fetus to extract oxygen from the maternal blood.

4. **Mechanism of Gas Exchange**: The movement of gases such as oxygen and carbon dioxide occurs based on concentration gradients. For the fetus to receive oxygen from the mother, its hemoglobin must be able to bind oxygen effectively, which is facilitated by its higher affinity.

5. **Conclusion**: Therefore, the correct statement regarding the hemoglobin of a human fetus is that it has a higher affinity for oxygen compared to adult hemoglobin. This adaptation is essential for the survival of the fetus during its development.

**Final Answer**: The hemoglobin of a human fetus has a higher affinity for oxygen than that of an adult.

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