Cell Membrane

  • Phospholipid bilayer
  • Cholesterol inside cell wall
  • Proteins extrude
    • on cytoplasm side, additional protein molecules are bound to proteins protruding from bilayer
    • On outside, short carbohydrate chains are linked to protruding proteins, in combination with the cell wall they play a role in cell interactions and transfers
  • Fluid-mosaic model says structure of cell membrane can move freely
  • Two basic embedded protein configurations have been found so far:
    • relatively simple rodlike structure consisting of an alpha helix embedded in the hydrophobic interior of the membrane, with less regular hydrophilic portions extending on either side. (See ill. 1.b)
    • The other is found in large, globular molecules with complex tertiary or quarternary that would result from repeated "passes" through the membrane.

  • Cell membrane of bacterial cells is much the same, except that it doesn't contain cholesterol

  • Eukaryotic membranes have similar membranes but different types of lipids.

  • Most membranes are 60% protein and 40% lipid, proteins have many different functions

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