Ap bio ch5membranes

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Ap bio ch5membranes

  1. 1. Membrane Structure and Function Chapter 5
  2. 2. Outline <ul><li>Membrane Models </li></ul><ul><ul><li>Fluid-Mosaic </li></ul></ul><ul><li>Plasma Membrane Structure and Function </li></ul><ul><ul><li>Protein Functions </li></ul></ul><ul><ul><li>Plasma Membrane Permeability </li></ul></ul><ul><ul><ul><li>Diffusion </li></ul></ul></ul><ul><ul><ul><li>Osmosis </li></ul></ul></ul><ul><ul><ul><li>Transport Via Carrier Proteins </li></ul></ul></ul><ul><li>Cell Surface Modifications </li></ul>
  3. 3. Membrane Models <ul><li>Fluid-Mosaic Model </li></ul><ul><ul><li>Membrane is a fluid phospholipid bilayer in which protein molecules are either partially or wholly embedded. </li></ul></ul>
  4. 4. Fluid-Mosaic Model
  5. 5. Plasma Membrane Structure and Function <ul><li>Plasma membrane separates internal environment from the external environment. </li></ul><ul><li>Hydrophilic polar heads face outside, and hydrophobic nonpolar tails face each other. </li></ul>
  6. 6. Plasma Membrane Structure and Function <ul><li>Proteins may be peripheral or integral. </li></ul><ul><ul><li>Peripheral proteins are found on the inner membrane surface. </li></ul></ul><ul><ul><li>Integral proteins are embedded in the membrane. </li></ul></ul>
  7. 7. Protein Functions <ul><li>Channel Proteins - Involved in passage of molecules through membrane. </li></ul><ul><li>Carrier Proteins - Combine with substance to aid in passage through membrane. </li></ul><ul><li>Cell Recognition Proteins - Help body recognize foreign substances. </li></ul>
  8. 8. Protein Functions <ul><li>Receptor Proteins - Allow molecule binding, causing protein to change shape and bring about cellular change. </li></ul><ul><li>Enzymatic Proteins - Carry out metabolic reactions directly. </li></ul>
  9. 9. Plasma Membrane Permeability <ul><li>Plasma membrane is differentially permeable. </li></ul><ul><ul><li>Passive Transport - No ATP requirement. </li></ul></ul><ul><ul><ul><li>Molecules follow concentration gradient. </li></ul></ul></ul><ul><ul><li>Active Transport - Requires carrier protein and ATP. </li></ul></ul>
  10. 10. Crossing Plasma Membrane
  11. 11. Diffusion <ul><li>Diffusion - Movement of molecules from a higher to a lower concentration until equilibrium is reached. </li></ul><ul><ul><li>Down concentration gradient </li></ul></ul><ul><li>A solution contains a solute (solid) and a solvent (liquid). </li></ul>
  12. 12. Diffusion
  13. 13. Osmosis <ul><li>Osmosis - Diffusion of water across a differentially (selectively) permeable membrane due to concentration differences. </li></ul><ul><ul><li>Osmotic pressure is the pressure that develops due to osmosis. </li></ul></ul><ul><ul><ul><li>The greater the osmotic pressure, the more likely water will diffuse in that direction. </li></ul></ul></ul>
  14. 14. Osmosis
  15. 15. Osmosis <ul><li>Isotonic Solution - Solute and water concentrations both inside and outside the membrane are equal. </li></ul><ul><li>Hypotonic Solution - Solution with a lower concentration of solute than the solution on the other side of the membrane. </li></ul><ul><ul><li>Cells placed in a hypotonic solution will swell. </li></ul></ul><ul><ul><ul><li>Lysis </li></ul></ul></ul>
  16. 16. Osmosis <ul><li>Hypertonic Solution - Solution with a higher concentration of solute than the solution on the other side of the membrane. </li></ul><ul><ul><li>Cells placed in a hypertonic solution will shrink. </li></ul></ul><ul><ul><ul><li>Plasmolysis </li></ul></ul></ul>
  17. 17. Transport by Carrier Proteins <ul><li>Carrier proteins combine with a certain molecules which are then transported through the membrane. </li></ul><ul><ul><li>Facilitated Transport </li></ul></ul><ul><ul><ul><li>Small molecules follow concentration gradient by combining with carrier proteins. </li></ul></ul></ul>
  18. 18. Transport by Carrier Proteins <ul><ul><li>Active Transport </li></ul></ul><ul><ul><ul><li>Small molecules move against their concentration gradient by combining with carrier proteins. </li></ul></ul></ul>
  19. 19. Membrane-Assisted Transport <ul><li>Large marcomolecules are transported into or out of the cell by vesicle formation. </li></ul><ul><ul><li>Exocytosis - Vesicles fuse with plasma membrane as secretion occurs. </li></ul></ul>
  20. 20. Membrane-Assisted Transport <ul><ul><li>Endocytosis - Cells take in substances by vesicle formation. </li></ul></ul><ul><ul><ul><li>Phagocytosis - Large, solid material. </li></ul></ul></ul><ul><ul><ul><li>Pinocytosis - Liquid or small, solid particles. </li></ul></ul></ul><ul><ul><ul><li>Receptor-Mediated - Specific form of pinocytosis using a coated pit. </li></ul></ul></ul>
  21. 22. Cell Surface Modifications <ul><li>Cell Surfaces in Animals </li></ul><ul><ul><li>Junctions Between Cells </li></ul></ul><ul><ul><ul><li>Adhesion Junctions </li></ul></ul></ul><ul><ul><ul><ul><li>Intercellular filaments between cells. </li></ul></ul></ul></ul><ul><ul><ul><li>Tight Junctions </li></ul></ul></ul><ul><ul><ul><ul><li>Form impermeable barriers. </li></ul></ul></ul></ul><ul><ul><ul><li>Gap Junctions </li></ul></ul></ul><ul><ul><ul><ul><li>Plasma membrane channels are joined (allows communication). </li></ul></ul></ul></ul>
  22. 23. Cell Surface Modifications <ul><ul><li>Extracellular Matrix </li></ul></ul><ul><ul><ul><li>Meshwork of polysaccharides and proteins in close association with the cell that produced them. </li></ul></ul></ul><ul><li>Plant Cell Walls </li></ul><ul><ul><li>Plants have freely permeable cell wall, with cellulose as the main component. </li></ul></ul><ul><ul><ul><li>Joined by plasmodesmata that spans cell wall and contains strands of cytoplasm that allow passage of material between cells. </li></ul></ul></ul>
  23. 24. Review <ul><li>Membrane Models </li></ul><ul><ul><li>Fluid-Mosaic </li></ul></ul><ul><li>Plasma Membrane Structure and Function </li></ul><ul><ul><li>Protein Functions </li></ul></ul><ul><ul><li>Plasma Membrane Permeability </li></ul></ul><ul><ul><ul><li>Diffusion </li></ul></ul></ul><ul><ul><ul><li>Osmosis </li></ul></ul></ul><ul><ul><ul><li>Transport Via Carrier Proteins </li></ul></ul></ul><ul><li>Cell Surface Modifications </li></ul>

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