Cell Membranes

841 views

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
841
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
9
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Cell Membranes

  1. 1. CELL MEMBRANES <ul><li>The Fluid-Mosaic Model </li></ul>This is an introduction to the structure and function of cell membranes. It is designed to be a self-contained unit with links to other, related material. www.freelivedoctor.com
  2. 2. THE FUNCTION OF CELL MEMBRANES <ul><li>Compartmentalization of tissues </li></ul><ul><li>Regulation of cell contents </li></ul><ul><li>Provides surface for enzymes, receptors, recognition, etc. </li></ul>It is thought by some that the spontaneous organization of membranes played an important role in the evolution of life . www.freelivedoctor.com
  3. 3. PHOSPHOLIPIDS: The “Backbone” of the Membrane Cartoon of a phospholipid molecule This cartoon depicts the basic amphipathic* structure common to all phospholipids * both polar and non-polar regions Fatty acids Glycerol plus polar side group www.freelivedoctor.com
  4. 4. WATER MOLECULES ARE POLAR <ul><li>Structure of water and the Cartoon version </li></ul><ul><li>Water is a dipole </li></ul>O H H + + d d/2 d/2 + Oxygen pulls electrons towards itself causing a charge imballance (d-) www.freelivedoctor.com
  5. 5. Water is a good solvent for polar molecules and ions - + - + - + - + - + Hydration Shells - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + www.freelivedoctor.com Na + Cl - - + - + - + - + - + - +
  6. 6. PHOSPHOLIPIDS <ul><li>Cartoon of a phospholipid molecule </li></ul>Polar head (Hydrophilic- likes water) Non-polar tail (Hydrophobic- hates water) www.freelivedoctor.com
  7. 7. OIL/WATER PARTITION: THE “KITCHEN” EXPERIMENT MIX OIL WATER AND TEST SUBSTANCE WATER CONCENTRATION OF TEST SUBSTANCE IN OIL/ CONCENTRATION OF TEST SUBSTANCE IN WATER = OIL WATER PARTITION COEFFICIENT (OWPC=K) K > 1 HYDROPHOBIC (NON-POLAR) K < 1 HYDROPHILIC (POLAR) www.freelivedoctor.com WAIT OIL
  8. 8. MIXING PHOSPHOLIPIDS AND WATER: Spontaneous Self-Organization www.freelivedoctor.com
  9. 9. MIXING PHOSPHOLIPIDS AND WATER: Spontaneous Self-Organization www.freelivedoctor.com
  10. 10. MIXING PHOSPHOLIPIDS AND WATER: Spontaneous Self-Organization Click ahead www.freelivedoctor.com
  11. 11. MIXING PHOSPHOLIPIDS AND WATER: Spontaneous Self-Organization www.freelivedoctor.com
  12. 12. Phospholipids plus water make a self-organizing system <ul><li>Low lipid/water ratio - micelles </li></ul><ul><li>High lipid/water ratio - lamellae </li></ul><ul><li>Single lamellae = bilayer or sheet </li></ul>www.freelivedoctor.com
  13. 13. Micelle Sheet www.freelivedoctor.com
  14. 14. The Black Lipid Membrane (BLM) <ul><li>Formed across a small hole in a teflon beaker using a sable artist’s brush </li></ul><ul><li>Viewed with an optical system </li></ul><ul><li>Looks like a soap bubble with large patches of black where the bilayer forms </li></ul><ul><li>Used as a laboratory model of the cell membrane </li></ul>www.freelivedoctor.com
  15. 15. The Black Lipid Membrane (BLM) <ul><li>Experimental Setup </li></ul>What you see Light Source Microscope Outer Beaker Inner Beaker www.freelivedoctor.com
  16. 16. Permeability of the BLM mol/sec-sq. cm. www.freelivedoctor.com
  17. 17. The Black Lipid Membrane Could be used to Show what else is in Cell Membranes <ul><li>It has too low permeability for ions- it needs protein and polypeptide to help them get through (channels and carriers) </li></ul><ul><li>It needs cholesterol for proper “fluidity” </li></ul><ul><li>It needs carbohydrate to provides cell recogtnition properties </li></ul>www.freelivedoctor.com
  18. 18. The membrane is fluid www.freelivedoctor.com
  19. 19. The membrane is fluid www.freelivedoctor.com
  20. 20. The membrane is fluid www.freelivedoctor.com
  21. 21. The membrane is fluid www.freelivedoctor.com
  22. 22. Cholesterol sits between fatty tails www.freelivedoctor.com
  23. 23. Proteins can span the bilayer Hydrophilic Hydrophobic www.freelivedoctor.com
  24. 24. The fluid-mosaic model <ul><li>Lipid bilayer </li></ul><ul><li>Cholesterol between tails </li></ul><ul><li>Protein, Glycoprotein, Lipoprotein “dissolved” in the lipid portion </li></ul>www.freelivedoctor.com
  25. 25. The fluid-mosaic model www.freelivedoctor.com
  26. 26. Channels and carriers are needed to get ions across the bilayer www.freelivedoctor.com
  27. 27. Channels and carriers are needed to get ions across the bilayer www.freelivedoctor.com
  28. 28. Cell Membranes Become Network Elements in Tissue Membranes <ul><li>Epithelia are tissue membranes made up of cells </li></ul><ul><li>Network Thermodynamics provides a way of modeling these composite membranes </li></ul><ul><li>Often more than one flow goes through the tissue </li></ul>www.freelivedoctor.com
  29. 29. An Epithelial Membrane in Cartoon Form: www.freelivedoctor.com
  30. 30. A Network Model of Coupled Salt and Volume Flow Through an Epithelium AM TJ BM BL CL PL CB PB CELL LUMEN BLOOD www.freelivedoctor.com
  31. 31. What to do now? <ul><li>Please contact me to tell me what your reaction to the presentation is. </li></ul><ul><li>If you wish to see how well you understood the presentation, try the SELF TEST. </li></ul>www.freelivedoctor.com

×