Plasma cell surface membrane

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  • Plasma cell surface membrane
    • Made of a thin layer of lipid (fat) molecules and protein molecules.
    • Controls what enters and exits the cell
      • the plasma membrane allows small, uncharged particles to pass through
      • protein channels and transporters control larger or charged particles
    • separates the cells contents from its external environment
    • partially permeable
    • some organelles inside the cell also are surrounded by a single membrane
      • eg) lysosomes
      • and some have a double membrane
        • eg) the nucleus, mitochondria and chloroplasts
          • this isolates the reactions in organelle from that in the cytoplasm
    • important in cell signalling
      • a substance produced- then docks into a receptor in the plasma membrane of another
    • allow electrical signals to pass along them
      • eg) membrane of the axon of a motor neurone
        • this transmits the action potentials from the CNS to a muscles
    • Cholesterol
      • lies alongside the phospholipids, making up bilayer
        • helps maintain fluidity
          • prevents it becoming too stiff in cold temps
          • or too fluid in high temps
  • Phospholipid-forms the bilayer
    • Provides a BARRIER to water-soluble substances, such as ions and molecules
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