Special surfaces for exchange

AS biology Special exchange surfaces

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  • Created by: lily
  • Created on: 30-10-11 16:51

Exchange surfaces appearance

  • Large surface area - more space for molecules to pass (folding walls& membranes)
  • Thin barrier- reduce diffusion distance
  • Fresh supply of molecules of 1 side - keep conc. high for osmosis
  • Removal of molecules on other side -keep conc. low for osmosis



  • small intestine (nutrients absorbed)
  • liver (sugars in blood adjusted)
  • root hairs of plants (minerals & H20 absorbed)
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Lungs as an organ of exchange


  • pair of inflatable structures in chest cavity

Air: Nose -->Trachea -->bronchi & bronchioles -->alveoli (walls of which= where exchange of gases takes place)

  • protected by ribs (breathing helped by movement of ribs & diaphragm

o2 passes from air in alveoli --> blood in capillaries

co2 passes from blood --> air in alveoli

adapted for exchange:

  • Large Surface Area
  • Barrier permeable to 02 & CO2
  • Thin barrier
  • Fresh supply of CO2 from blood on one side, fresh supply of 02 from breathing on other side
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Tissues in the lungs

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