A-LevelBiologyGas exchange9700/12 · Oct/Nov 2017 · Q341 Mark
A good gas exchange system maintains a steep diffusion gradient, has a large total surface area and a short diffusion distance. Which feature of the human gas exchange system helps to maintain a steep diffusion gradient?
Alarge number of alveoli are present in each lung.
BAlveoli walls contain elastic fibres allowing expansion.
CThe air brought into the alveoli by ventilation is high in oxygen.
DThe endothelium of the capillary wall is made of flattened cells.
✓ Correct answer
C: The air brought into the alveoli by ventilation is high in oxygen.
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