Membrane Structure and Function<br />
Plasma Membrane<br />The membrane at the boundary of every cell.<br />Functions as a selective barrier for the passage of ...
Membrane Composition<br />Lipids<br />Proteins<br />
Fluid Mosaic Model<br />Refers to the way the lipids and proteins behave in a membrane.<br />
“Fluid”<br />Refers to the lipid bilayer.<br />Molecules are not bonded together, so are free to shift.<br /> Must remain ...
“Mosaic”<br />Proteins: float in a sea of lipids.<br />Proteins form a collage or mosaic pattern that shifts over time.<br />
Protein Function in Membranes<br />Transport.<br />Enzymatic activity.<br />Receptor sites for signals.<br />Cell adhesion...
Types of Membrane Proteins<br />Integral - inserted into the lipid bilayer.<br />Peripheral - not embedded in the lipid bi...
Membranes are Bifacial<br />The lipid composition of the two layers is different.<br />The proteins have specific orientat...
Question<br />How do materials get across a cell's membrane?<br />
Problems<br />Lipid bilayer is hydrophobic.  Hydrophilic materials don't cross easily. <br />Large molecules don't cross e...
Mechanisms<br />1.  Passive Transport<br />2.  Active Transport<br />
Passive Transport<br />Movement across membranes that does NOT require cellular energy.<br />
Types of Passive Transport<br />1.  Diffusion<br />2.  Osmosis<br />3.  Facilitated Diffusion<br />
Diffusion<br />The net movement of atoms, ions or molecules down a concentration gradient.<br />Movement is from: <br />  ...
Equilibrium<br />When the concentration is equal on both sides.  <br />There is no net movement of materials.<br />
Factors that Effect Diffusion<br />1.  Concentration<br />2.  Temperature<br />3.  Pressure<br />4.  Particle size<br />5....
Osmosis<br />Diffusion of water.<br />Water moving from an area if its high concentration to an area of its low concentrat...
Tonicity<br />The concentration of water relative to a cell. <br />1.  Isotonic (same)<br />2.  Hypotonic (below)<br />3. ...
Isotonic <br />Isosmotic solution.<br />Cell and water are equal in solute concentration.<br />No net movement of water in...
Hypotonic<br />Hypoosmotic solution<br />Cell's water is lower than the outside water (more solutes).<br />Water moves int...
Hypertonic<br />Hyperosmotic solution<br />Cell's water is higher than the outside water (less solutes)<br />Water moves o...
Facilitated Diffusion<br />Transport protein that helps materials through the cell membrane. <br />Doesn't require energy ...
Active Transport<br />Movement across membranes that DOES require cellular energy.<br />
Types of Active Transport<br />1.  Carrier-Mediated <br />2.  Endocytosis<br />3.  Exocytosis<br />
Carrier-Mediated Transport<br />General term for the active transport of materials into cells AGAINST the concentration gr...
Examples<br />1. Na+- K+ pump<br />2. Electrogenic or H+ pumps<br />3. Cotransport<br />
Exocytosis<br />Moves bulk material out of cells.<br />Example - secretion of enzymes.<br />
Endocytosis<br />Moves bulk materials into cells.<br />Several types known.<br />
Types<br />1.  Pinocytosis - liquids<br />2.  Phagocytosis - solids<br />3.  Receptor Mediated - uses receptors to "catch"...
The Cell Membrane
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The Cell Membrane

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Transcript of "The Cell Membrane"

  1. 1. Membrane Structure and Function<br />
  2. 2. Plasma Membrane<br />The membrane at the boundary of every cell.<br />Functions as a selective barrier for the passage of materials in and out of cells.<br />
  3. 3. Membrane Composition<br />Lipids<br />Proteins<br />
  4. 4. Fluid Mosaic Model<br />Refers to the way the lipids and proteins behave in a membrane.<br />
  5. 5. “Fluid”<br />Refers to the lipid bilayer.<br />Molecules are not bonded together, so are free to shift.<br /> Must remain "fluid" for membranes to function.<br />
  6. 6. “Mosaic”<br />Proteins: float in a sea of lipids.<br />Proteins form a collage or mosaic pattern that shifts over time.<br />
  7. 7.
  8. 8. Protein Function in Membranes<br />Transport.<br />Enzymatic activity.<br />Receptor sites for signals.<br />Cell adhesion.<br />Cell-cell recognition.<br />Attachment to the cytoskeleton.<br />
  9. 9.
  10. 10. Types of Membrane Proteins<br />Integral - inserted into the lipid bilayer.<br />Peripheral - not embedded in the lipid bilayer, but are attached to the membrane surface.<br />
  11. 11.
  12. 12. Membranes are Bifacial<br />The lipid composition of the two layers is different.<br />The proteins have specific orientations. <br />Carbohydrates are found only on the outer surface.<br />
  13. 13. Question<br />How do materials get across a cell's membrane?<br />
  14. 14. Problems<br />Lipid bilayer is hydrophobic. Hydrophilic materials don't cross easily. <br />Large molecules don't cross easily. Too big to get through the membrane.<br />
  15. 15. Mechanisms<br />1. Passive Transport<br />2. Active Transport<br />
  16. 16. Passive Transport<br />Movement across membranes that does NOT require cellular energy.<br />
  17. 17. Types of Passive Transport<br />1. Diffusion<br />2. Osmosis<br />3. Facilitated Diffusion<br />
  18. 18. Diffusion<br />The net movement of atoms, ions or molecules down a concentration gradient.<br />Movement is from: <br /> High Low<br />
  19. 19.
  20. 20. Equilibrium<br />When the concentration is equal on both sides. <br />There is no net movement of materials.<br />
  21. 21. Factors that Effect Diffusion<br />1. Concentration<br />2. Temperature<br />3. Pressure<br />4. Particle size<br />5. Mixing<br />
  22. 22. Osmosis<br />Diffusion of water.<br />Water moving from an area if its high concentration to an area of its low concentration.<br />No cell energy is used.<br />
  23. 23. Tonicity<br />The concentration of water relative to a cell. <br />1. Isotonic (same)<br />2. Hypotonic (below)<br />3. Hypertonic (above)<br />
  24. 24.
  25. 25. Isotonic <br />Isosmotic solution.<br />Cell and water are equal in solute concentration.<br />No net movement of water in or out of the cell.<br />No change in cell size.<br />
  26. 26. Hypotonic<br />Hypoosmotic solution<br />Cell's water is lower than the outside water (more solutes).<br />Water moves into the cell. <br />Cell swells, may burst or the cell is turgid.<br />
  27. 27. Hypertonic<br />Hyperosmotic solution<br />Cell's water is higher than the outside water (less solutes)<br />Water moves out of the cell. <br />Cell shrinks or plasmolysis occurs.<br />
  28. 28. Facilitated Diffusion<br />Transport protein that helps materials through the cell membrane. <br />Doesn't require energy (ATP).<br />Works on a downhill concentration gradient.<br />
  29. 29.
  30. 30. Active Transport<br />Movement across membranes that DOES require cellular energy.<br />
  31. 31. Types of Active Transport<br />1. Carrier-Mediated <br />2. Endocytosis<br />3. Exocytosis<br />
  32. 32. Carrier-Mediated Transport<br />General term for the active transport of materials into cells AGAINST the concentration gradient.<br />Movement is: <br /> low high<br />
  33. 33. Examples<br />1. Na+- K+ pump<br />2. Electrogenic or H+ pumps<br />3. Cotransport<br />
  34. 34. Exocytosis<br />Moves bulk material out of cells.<br />Example - secretion of enzymes.<br />
  35. 35. Endocytosis<br />Moves bulk materials into cells.<br />Several types known.<br />
  36. 36. Types<br />1. Pinocytosis - liquids<br />2. Phagocytosis - solids<br />3. Receptor Mediated - uses receptors to "catch" specific kinds of molecules.<br />

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