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Cell Membrane


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Cell Membrane

  1. 1. The Cell Membrane FOS 3 Infectious Disease Unit
  2. 2. Composition of Cell Membrane Cell Membranes are NOT all identical, but have FOUR common parts:  Lipid Bilayer  Transmembrane Protein  Network of supporting fibers  Glycoproteins  On outside of cell  Cell Surface has a carbohydrate coat to prevent sticking.
  3. 3. Lipid Foundation- Phospholipid BilayerConsist of a: Glycerol backbone Fatty Acid tails (nonpolar/ hydrophobic) Phosphorylated alcohol (polar/hydrophilic)
  4. 4. Lipid Foundation- PhospholipidsFatty Acid side is NONPOLAR Nonsoluble in waterPhophate side is POLAR Soluble in water
  5. 5. Lipid Bilayer Creates barrier to water soluble molecules Inside (tails) of bilayer are nonpolar and therefore insoluble to water Lipid bilayer is fluid, yet stable.
  6. 6. Fluid Mosaic Model
  7. 7. If you want more information of this go to: 2/membrane.htmHistory of the Fluid Mosaic Model
  8. 8. Controls the fluidity of the Cell MembraneTemperatureLength of tails and kinks in tailsCholesterol
  9. 9. How do things get through if there is a barrier? Simple diffusion. Through “kinks” in the fatty acid tails Closely aligned tails have C-C (single bonds) C=C (double/triple bonds) cause “kinks”
  10. 10. Transmembrane Proteins extend across lipid bilayer These proteins can have both a polar and a nonpolar region. Enables them to be embedded in the nonpolar (hydrophobic) area of the membrane Polar regions are anchored in the water Provide CHANNELS into the cell but only for selected items.
  11. 11. Proteins act as Cell Identification MarkersLipids and proteins within the membrane may have a carbohydrate chain attachedThese glycolipids and glycoproteins often function as cell ID markers, allowing cells to identify other cellsThis is particularly important in the immune system where cells patrolling the body’s tissues identify and destroy foreign invaders such as bacteria or viruses.
  12. 12. Cell Surface ReceptorsIt’s shape fits signal molecules, such as hormones.Receptors enable cells to detect hormones and a variety of other chemicals in their environmentThe binding of a molecule and a receptor initiates a chemical change within the cell.
  13. 13. Channel Proteins In some cases the channel proteins simply act as a passive pore. Molecules will randomly move through the opening in a process called diffusion. This requires no energy, molecules move from an area of high concentration to an area of low concentration.
  14. 14. Carrier ProteinsThey do not extend through the membraneThey bond and drag molecules through the lipid bilayer and release them on the opposite side.
  15. 15. Proteins used to attach CytoskeletonReceptor proteins help to attach the cytoskeleton inside the cell.
  16. 16. Cholesterol in Cell Membrane The phospholipid bilayer also contains cholesterol molecules. This gives the layer greater strength, more flexibility, less fluid and less permeable to ions and monosaccharides.
  17. 17. Major Histocompatibility ComplexUnique to every individual Except identical twinsConsists of proteins that attach to exterior cells and antigensAllows T-Cells in the immune system to recognize and attack foreign cellsGlycolipids also differentiate between tissues of same individual A, B, AB and O blood group markers.
  18. 18. Membrane Protein Functions
  19. 19. Membrane Protein Functions