Roles of membranes

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  • Created by: Jasmin
  • Created on: 20-10-14 20:28
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  • Roles
    • Plasma membranes
      • Partially permable -let some molecules in through but not others
      • Controls which substances enter and leaves the cell
      • They allow recognition by other cells (e.g. the cells of the immune system)
    • Membranes within cells
      • Membranes around organelles divides the cell into different compartments making the function more efficient.
      • They can form vesicles to transport substances between different areas of the cell
      • They control which substances ener and leave the organelle (e.g. RNA leaves the nucleus via the nuclear membrane)
    • Phospholipids
      • Forms a barrier to dissolved substance
      • The head is hydrophillic -attracts water. The tail is hydrophobic -repels water
      • The center of the bilayer is hydrophobic. So the membrane does not allow water soluble substances (like ions) through it
    • Cholestrol
      • Gives the membrane stability
      • Cholestrol molecules fit beteen the phospholipids, causing them to pack more closely together. This makes the membrane less fluid and more rigid
    • Proteins
      • Channel proteins allow small and charged particles through
      • Carrier proteins transport molecules and ions across the membrane by active transport and facilitated diffusion
      • Proteins act as receptors for molecules (e.g hormones) inc ell signaling. When a molecule binds to the protein, a chemical reaction is triggered inside the cell
    • Glucolipids and Glucoproteins
      • Acts as receptors for messenger molecules
      • Stabalises the membrane for forming hydrogen bonds with surrounding water molecules
      • They are also sites where drugs hormones and antibodies bond
      • They are also antigens -cell surface molecules involved in the immune response.


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