Answer: Damaged alveolar walls merge, cutting the surface area for diffusion.
- A The diaphragm loses most of its ability to contract in most reference accounts
- B Damaged alveolar walls merge, cutting the surface area for diffusion
- C The trachea becomes blocked by excess mucus build-up as frequently documented
- D Hemoglobin gradually loses its ability to bind oxygen under normal conditions
Correct answer: B. Damaged alveolar walls merge, cutting the surface area for diffusion
Explanation: Emphysema involves breakdown of alveolar walls, which reduces the surface area available for gas exchange and impairs efficient diffusion of O<sub>2</sub> and CO<sub>2</sub>.
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.