Fluid boundaries

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  • Created by: Steff06
  • Created on: 03-04-16 11:51
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  • Fluid boundaries
    • Roles of membranes:
      • Separating cell contents from the outside environment. Separating cell components from the cell cytoplasm. Cell recognition and signalling. Holding components of metabolic pathways in pace. Regulating transport of materials into or out of cells.
    • Phosphate head is HYDROPHILIC, whilst the 2 fatty acid tails are HYDROPHOBIC. Membranes are PARTIALLY permeable.
    • Rarely the phospholipid molecules may 'flip-flop' from one layer to another. The hydrophilic head cannot pass through the hydrophobic region which gives the bilayer some STABILITY.
    • All membranes are permeable to water molecules, because water molecules can diffuse through the lipid bilayer. Membranes containing AQUAPORINS are even more permeable.
    • PARTIALLY PERMEABLE membranes are membranes that are permeable to water and some solutes.
    • Fluid mosaic model - LIPID molecules give FLUIDITY and PROTEINS in the membrane give it a mosaic appearance.
    • Features of a fluid mosaic model:
      • A bilayer of phospholipid forming the basic structure. Protein molecules floating in the bilayer, some freely, some bound to other components.
        • Extrinsic proteins partially embedded in the bilayer on inside/outside face. Intrinsic proteins spanning the bilayer.


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