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Smoking damage and gas exchange
Smoking can damage the lungs in different ways. Figure 6 shows alveoli from the lungs of two people.
Person A and person B do the same exercise.
Explain why person B breathes much faster than person A during the exercise.
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Marking points
- 1 Explains that faster/deeper breathing is needed to take in more oxygen.
- 2 Uses Figure 6 to identify person B's smaller alveolar surface area.
- 3 Links the smaller surface area to less oxygen entering the blood / oxygenating haemoglobin.
- 4 Links reduced oxygen delivery to less aerobic respiration or more anaerobic respiration/lactic acid/oxygen debt.
Full-mark answer
Smoking has reduced the folded surface of person B's alveoli, so person B has a smaller surface area for gas exchange. Less oxygen diffuses into the blood, leaving less oxygen available for aerobic respiration during exercise. Person B therefore has to breathe faster or deeper to take in more oxygen; otherwise anaerobic respiration and lactic acid production increase.
Why this answer loses marks
Person B makes less energy, so exercise is harder.
Energy is released, not made; the answer also needs the smaller surface area, reduced oxygen uptake, and faster breathing response.