Answer: Hypoxia, which raises erythropoietin secretion from the kidney.
- A A fall in carbon dioxide levels within the blood
- B Hypoxia, which raises erythropoietin secretion from the kidney
- C Increased atmospheric pressure acting directly on bone marrow
- D Faster hemoglobin breakdown occurring in the spleen
Correct answer: B. Hypoxia, which raises erythropoietin secretion from the kidney
Explanation: Low oxygen levels (hypoxia) at high altitude stimulate the kidneys to secrete more erythropoietin, which increases red blood cell production to improve oxygen-carrying capacity.
The S-shaped (sigmoid) curve reflects cooperative binding between Hb's four O₂ sites; the Bohr effect shifts the whole curve to the right under conditions found in actively respiring tissue (more CO₂, more acid, more heat), making haemoglobin release oxygen more readily exactly where it's needed.
Concept context
The mechanics of breathing, lung volumes, gas transport in blood, the Bohr effect, and respiratory regulation.