Answer: tidal volume.
- A tidal volume
- B vital capacity
- C residual volume
- D total lung capacity
Correct answer: A. tidal volume
Explanation: Tidal volume is the air moved in a normal, relaxed breath (about 500 mL).
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.