Biology 9700 · AS & A Level · Movement into and out of cells

Movement into and out of cells — practice question

An oxygen molecule moves by diffusion from the air within an alveolus, through cells, to haemoglobin in a red blood cell. What is the minimum number of cell surface membranes that this molecule must cross?

  • A2
  • B3
  • C4
  • D5

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