Cell-surface membrane

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  • Created by: Alice
  • Created on: 12-01-14 16:30
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  • Cell Surface Membrane
    • All membranes are known as plasma membranes
      • Cell boundary; allow different conditions in/out of cell. Control entry and exit
      • Made up of carbohydrate, lipid, and protein
      • Effective as phospholipids are polar and can form a bi-layer sheet
    • Phospholipids form a bilayer sheet
      • Allow lipid-soluble substances to enter/leave cell
      • Make membranes flexible
      • Prevent water-soluble substances entering/leaving cell
      • 1 layer: hydrophilic heads interacting with water in cell cytoplasm
      • 1 layer: hydrophilic heads pointing out, interacting w/ water around cells
      • Hydrophobic tails protected from water by pointing inwards
    • Proteins are embedded in the bilayer
      • Extrinsic proteins
        • On surface, never extend across bilayer
        • Give support or act as cell receptors
          • Act as receptors
      • Intrinsic proteins
        • Span across the bilayer
        • Act as carriers, others are enzymes
          • Act as carriers for water-soluble substances
      • Structural support
        • Give support or act as cell receptors
          • Act as receptors
      • Act as carriers for water-soluble substances
      • Form ion channels for active transport
      • Form recognition sites
    • Fluid-mosaic model of the CSM
      • Fluid: flexible structure, always changing shape - molecules can move relatively
      • Mosaic: embedded proteins vary in shape, size, and pattern
  • All membranes are known as plasma membranes
    • Cell boundary; allow different conditions in/out of cell. Control entry and exit
    • Made up of carbohydrate, lipid, and protein
    • Effective as phospholipids are polar and can form a bi-layer sheet

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