Movement of molecules in and out of cells

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  • Created by: Uswa
  • Created on: 23-03-13 14:33
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  • Movement of molecules in and out of cells
    • Dissolved Substances
      • Dissolved substances move by diffusion and by active transport.
      • OSMOSIS
        • Is the diffusion of water molecules from a dilute to a more concentrated solution, through a partially permeable membrane that allows passage of water molecules.
        • Water often moves across boundaries by osmosis.
        • Differences in concentration of the solutions INSIDE and OUTSIDE of a cell--> cause water to move into our out of cells by osmosis.
    • Soft drinks
      • Many soft drinks contain WATER, SUGAR and IONS.
      • Most drinks contain SUGARS to replace the sugar used in ENERGY    RELEASE during the activity
      • They contain WATER and IONS to replace the ones lost during SWEATING.
      • If water and ions aren't replaced, ion/water balance of body is disturbed
        • And cells  don't work effectively
    • Active Transport
      • Substances are sometimes absorbed against a concentration gradient
        • Needs use of energy from respiration and is called ACTIVE TRANSPORT.
      • Allows cells to absorb ions from very dilute solutions
    • Adaptations
      • Gas and solute exchange surfaces are  adapted to maximise effectiveness.
      • Effectiveness of exchange surface is increased by
        • Having a large surface area
        • Being thin- Short diffusion path
        • [In animals]
          • Having efficient and constant blood supply
          • Being ventilated (For GASEOUS exchange)
      • Size & complexity of an organism increases the difficulty of exchanging materials


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