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Features of A Specialised Exchange Surface

Exchange Surfaces:
  • should have a large surface area relative to the volume of the organism
  • should be very thin so that the diffusion distance is short.should have a selectively permeable membrane to allow material to crossshould have movement of the environmental medium to maintain a diffusion gradient.
    • should have a transport system to ensure the movement of the internal medium to maintain a diffusion gradient and transport the materials.Exchange surfaces are thin so that they have a short diffusion distance. They are therefore delicate and are usually located within the organism e.g. alveoli in mammalian lungs.

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Specification: AQA Biology (7401), AS-level, 3.3.2 Gas exchange. Topic: Exchange of Gases.

Key terms in this lesson

diffusion
The net passive movement of molecules or ions from a region of higher concentration to a region of lower concentration, down a concentration gradient.
alveolus
A tiny, thin-walled air sac in the lungs, surrounded by capillaries, that is the site of gas exchange.

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