Membrane Structure and Function

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Membrane Structure and Function

  1. 1. Chapter 7 Membrane Structure and Function
  2. 2. Figure 7-01
  3. 4. LE 7-3 Hydrophilic region of protein Hydrophobic region of protein Phospholipid bilayer
  4. 5. LE 7-2 Hydrophilic head Hydrophobic tail WATER WATER
  5. 6. LE 7-5 Lateral movement (~10 7 times per second) Flip-flop (~ once per month) Viscous Movement of phospholipids Fluid Unsaturated hydrocarbon tails with kinks Membrane fluidity Saturated hydro- carbon tails Cholesterol Cholesterol within the animal cell membrane
  6. 7. LE 7-7 Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Microfilaments of cytoskeleton Cholesterol Integral protein Peripheral proteins CYTOPLASMIC SIDE OF MEMBRANE EXTRACELLULAR SIDE OF MEMBRANE Glycolipid
  7. 8. LE 7-9a Enzymes Signal Receptor ATP Transport Enzymatic activity Signal transduction
  8. 9. LE 7-9b Glyco- protein Cell-cell recognition Intercellular joining Attachment to the cytoskeleton and extra- cellular matrix (ECM)
  9. 10. LE 7-8 EXTRACELLULAR SIDE N-terminus C-terminus CYTOPLASMIC SIDE  Helix
  10. 11. LE 7-10 Plasma membrane: Cytoplasmic face Extracellular face Transmembrane glycoprotein Plasma membrane: Secreted protein Vesicle Golgi apparatus Glycolipid Secretory protein Transmembrane glycoproteins ER
  11. 12. LE 7-7 Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Microfilaments of cytoskeleton Cholesterol Integral protein Peripheral proteins CYTOPLASMIC SIDE OF MEMBRANE EXTRACELLULAR SIDE OF MEMBRANE Glycolipid Activity: Selectively Permeable Membranes
  12. 14. LE 7-11a Molecules of dye Membrane (cross section) WATER Net diffusion Net diffusion Equilibrium Diffusion of one solute
  13. 15. LE 7-11b Net diffusion Net diffusion Equilibrium Diffusion of two solutes Net diffusion Net diffusion Equilibrium Activity: Diffusion
  14. 16. LE 7-12 Lower concentration of solute (sugar) Higher concentration of sugar Same concentration of sugar Selectively permeable mem- brane: sugar mole- cules cannot pass through pores, but water molecules can H 2 O Osmosis Activity: Osmosis
  15. 17. Water Potential <ul><li>Ψ = Ψ s + Ψ p </li></ul><ul><li>solute pressure </li></ul><ul><li> potential potential </li></ul><ul><li>Ψ s = -iCRT </li></ul><ul><li>i = ionization constant </li></ul><ul><li> (usually 1) </li></ul><ul><li>C = Molarity (M) </li></ul><ul><li>R = gas constant (0.0821) </li></ul><ul><li>T = temp in Kelvins (ºC + 273) </li></ul>Ψ p is zero in an open system
  16. 20. LE 7-13 Animal cell Lysed H 2 O H 2 O H 2 O Normal Hypotonic solution Isotonic solution Hypertonic solution H 2 O Shriveled H 2 O H 2 O H 2 O H 2 O Plant cell Turgid (normal) Flaccid Plasmolyzed Activity: Osmosis
  17. 21. LE 7-14 Filling vacuole 50 µm 50 µm Contracting vacuole
  18. 22. LE 7-15a EXTRACELLULAR FLUID Channel protein Solute CYTOPLASM
  19. 23. LE 7-15b Carrier protein Solute Activity: Facilitated Diffusion
  20. 24. LE 7-17 Diffusion Facilitated diffusion Passive transport ATP Active transport
  21. 25. LE 7-16 Cytoplasmic Na + bonds to the sodium-potassium pump CYTOPLASM Na + [Na + ] low [K + ] high Na + Na + EXTRACELLULAR FLUID [Na + ] high [K + ] low Na + Na + Na + ATP ADP P Na + binding stimulates phosphorylation by ATP. Na + Na + Na + K + Phosphorylation causes the protein to change its conformation, expelling Na + to the outside. P Extracellular K + binds to the protein, triggering release of the phosphate group. P P Loss of the phosphate restores the protein’s original conformation. K + is released and Na + sites are receptive again; the cycle repeats. K + K + K + K + K + Activity: Active transport
  22. 27. LE 7-18 H + ATP CYTOPLASM EXTRACELLULAR FLUID Proton pump H + H + H + H + H + + + + + + – – – – –
  23. 28. LE 7-19 H + ATP Proton pump Sucrose-H + cotransporter Diffusion of H + Sucrose H + H + H + H + H + H + + + + + + + – – – – – –
  24. 29. Activity: Exocytosis & Endocytosis
  25. 30. LE 7-20a CYTOPLASM Pseudopodium “ Food” or other particle EXTRACELLULAR FLUID Bacterium Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM) Pseudopodium of amoeba 1 µm Food vacuole PHAGOCYTOSIS
  26. 31. LE 7-20b Plasma membrane Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM). 0.5 µm Vesicle PINOCYTOSIS
  27. 32. LE 7-20c Receptor RECEPTOR-MEDIATED ENDOCYTOSIS Ligand Coated pit Coated vesicle Coat protein Coat protein Plasma membrane 0.25 µm A coated pit and a coated vesicle formed during receptor- mediated endocytosis (TEMs).

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