A-LevelBiologyGas exchange9700/12 · Feb/Mar 2023 · Q361 Mark
Two of the requirements of an efficient gas exchange system are a large surface area and a short diffusion distance. Which row correctly describes how alveoli are adapted to meet these requirements?
Aelastin fibres prevent the alveolus wall from collapsing; an extracellular layer inside the alveolus wall contains blood capillaries
Bgases dissolve in a layer of liquid to speed up diffusion; alveolar walls are next to capillaries
Calveoli are folded and interconnected; walls of alveoli are only one cell thick
Dwalls of alveoli are formed of squamous epithelial cells; red blood cells are very close to capillary walls
✓ Correct answer
C: alveoli are folded and interconnected; walls of alveoli are only one cell thick
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