Special surfaces for exchange

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  • Created by: Steff06
  • Created on: 08-04-16 10:09
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  • Exchange surfaces
    • Some substances needed to stay alive such as: OXYGEN for aerobic respiration, GLUCOSE for energy, PROTEINS for growth and repair, FATS to make membranes+to be energy store, WATER, MINERALS to maintain water potential+help enzyme action.
    • Organisms get hold of these substances by either ABSORBING them from their surrounding environment, or MAKE them in their CYTOPLASM as part of cell metabolism.
    • Living things need to remove waste products such as: CARBON DIOXIDE, OXYGEN, wastes e.g. AMMONIA/UREA which contain excess nitrogen.
    • All good exchange surfaces have:
      • A LARGE surface area to provide more space for molecules to pass through.
      • THIN BARRIER to reduce diffusion distance.
      • FRESH SUPPLY of molecules on one side to keep the concentration high.
      • REMOVAL of required molecules on one side to keep the concentration LOW.
    • Thin barrier, fresh supply of nutrients and removal of required molecules are important to MAINTAIN a steep DIFFUSION GRADIENT.
    • Examples of specialised exchange surfaces are: ALVEOLI in the LUNGS, SMALL INTENSTINE where nutrients are absorbed, LIVER, where levels of sugars in the blood are adjusted, ROOT HAIR CELLS of plants where water and minerals are absorbed, HYPHAE of FUNGI where nutrients are absorbed.


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