Answer: Lets hemoglobin release more oxygen at a given partial pressure.
- A Raises hemoglobin's affinity for carbon monoxide instead
- B Lets hemoglobin bind oxygen more tightly in muscle capillaries
- C Lets hemoglobin release more oxygen at a given partial pressure
- D Stops further oxygen unloading at the tissue level
Correct answer: C. Lets hemoglobin release more oxygen at a given partial pressure
Explanation: A rightward-shifted curve (favoured by raised CO<sub>2</sub>, H+, and temperature during exercise) reflects lower hemoglobin-O<sub>2</sub> affinity, so more oxygen is unloaded to meet the higher demand of active tissues.
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.