A Levels Biology (9700)•9700/13/M/J/21
Explanation
High-altitude acclimatization via increased erythropoiesis
Steps:
- Low oxygen at high altitudes causes hypoxia, detected by kidney cells.
- Kidneys release erythropoietin (EPO) hormone in response.
- EPO stimulates bone marrow to produce more red blood cells (RBCs).
- Increased RBCs enhance total blood oxygen-carrying capacity.
Why C is correct:
- Erythropoietin directly boosts RBC production, raising their count per mm³ to transport more oxygen, as defined in hypoxic physiological adaptation.
Why the others are wrong:
- A: Hemoglobin concentration within each RBC stays fixed at about 34% by weight.
- B: Each hemoglobin molecule's oxygen-binding sites remain unchanged at four per molecule.
- D: Hemoglobin's oxygen release rate adjusts via Bohr effect but isn't the primary acclimatization mechanism.
Final answer: C
Topic: Transport of oxygen and carbon dioxide
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