cell membrane and transport

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  • Cell membrane and transport
    • Cell membrane
      • Phospholipids
        • Arranged in a bilayer, different phospholipids have different fatty acids changing the strength and flexibility
        • cholesterol links the fatty acids, giving stability and strength
      • Proteins
        • One side to the other - integral proteins. Sit on the surface - peripheral proteines
        • hydrophilic molecules prevent them flipping
        • Transport proteins
          • Transport of small molecules mostly takes place in integral proteins
          • Includes facilitated and active transport
        • Receptor proteins
          • Outside surface and have a specific binding site
          • Binding triggers the event inside the cell
        • Recognition proteines
          • Cell recognition
        • Structural proteines
          • Inside surface, attached to cytoskeleton
          • Maintain or change cells shape
      • Carbohydrates
        • Outer surface attached to membrane proteins or phospholipids
    • Osmosis
      • Each solute molecule in a solution attracts a hydrogen shell
      • Water potential
        • Concentration of free water, pure water is 0, so everything is 0 or <0
      • Cells
        • Isotonic - equal water potential
        • Hypertonic - lower water potential than cell
          • Plant cell - cytoplasm shrinks from cell wall (plasmolyses)
          • Animal - shrinks (cenerates)
        • Hypotonic - lower water potential than cell
          • Animal - swells and bursts (lysis)
          • Swells and becomes turgid
    • Facilitated diffusion
      • Channel proteins
        • Co-transport. two molecules at one, both must be present
        • Substance binds at high concentration and is released at low.
      • Carrier proteins
        • Water filled pore/channel
        • Allows charged substances through
        • Gated
    • Active transport
      • Pumping substances through a protein pump up a concentration gradient
      • ATP
        • Hydrolyse ATP back to ADP + Pand uses the energy to change its shape, allowing substances to pass through
        • Synthesised from ADP + phosphate


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