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Chapter 11

Chapter 11. Biological Membranes: Part 1. Membranes. Part 1 and 2 Learning Goals: To Know. The function of biological membranes The structure and composition membranes and their molecules Dynamics of membranes Structure and function of membrane proteins

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Chapter 11

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  1. Chapter 11 Biological Membranes: Part 1

  2. Membranes Part 1 and 2 Learning Goals: To Know • The function of biological membranes • The structure and composition membranes and their molecules • Dynamics of membranes • Structure and function of membrane proteins • Transport across biological membranes

  3. Why are TEMs of membranes always light in the middle and dark on the sides? 50 – 80 Å Thick EOC Problem 5 has to do with the length of a fatty acid: how does this play into the thickness of this membrane?

  4. Cells Are Loaded with Membranes What’s the answer to the previous thought question?

  5. Major Membrane Lipids

  6. Membrane Lipid Composition – Rat Hepatocyte

  7. Fluid Mosaic Model

  8. Lipids aggregate into structures in water • Structures formed depend on: • type of lipid • concentration • Micelles • Liposomes • Bilayers

  9. Lipids in Water EOC Problem 3 … Number of SDS moleucles/micelle. You will need to calculate the MW of dodecyl-sulfate.

  10. Asymmetric Distribution of P-lipids in Erythrocyte Membrane

  11. Membrane composition and asymmetry

  12. Membrane Asymmetry Derived in ER

  13. Functions of Proteins in Membranes • Receptors: detecting signals from outside • Light (opsin) • Hormones (insulin receptor) • Neurotransmitters (acetylcholine receptor) • Pheromones (taste and smell receptors) • Channels, gates, pumps • Nutrients (maltoporin) • Ions (K-channel) • Neurotransmitters (serotonin reuptake protein) • Enzymes • Lipid biosynthesis (some acyltransferases) • ATP synthesis (F0F1 ATPase/ATP synthase)

  14. Extraction of Membrane Proteins

  15. Glycophorin – Transmembrane Protein Tetra-Saccharides, N-linked Tetra-Saccharides, O-linked

  16. Six Types of Integral Membrane Proteins

  17. Bacteriorhodopsin

  18. Bacteriochlorophyll – Reaction Center Chlorophylls in Red

  19. Great Illustration of Phospholipid as a Fluid Sec A (chaperone) in blue ribbon. Cytoplasmic side with ATP (bright light) Sec YE in Cream Space-filling cut away to show channel Transported protein in red thread

  20. Another Great Illustration of Phospholipid as a Fluid G Protein – major signaling protein, next Chapter.

  21. Phospholipid Associated with Isolated Membrane Proteins Sheep Aquaporin Fo Portion of V type Na-ATPase

  22. Hydropathy Plots

  23. Remember Hydropathic Index? Non Polar R groups have Positive Hydropathic Indices Y and W are negative

  24. Polar Amino Acids have Negative Hydropathic Indices

  25. Hydropathy Index Calculated from a Moving -Window of 7 to 20 Amino Acids

  26. Transmembrane Proteins – Positions of Y and W. Polar R – groups are Blue Y is Orange W is Red

  27. Membrane Spanning Regions can also be Beta-Barrel Structure

  28. Another Great Illustration showing the Membrane as a Fluid Surface of a B-cell showing the B-cell Receptor (purple, mono-valentIgM) binding to an HIV particle.

  29. Sided Proteins Anchored by Fatty Acids (Inside)

  30. Membranes can transition from Gels to Fluids a. Gel State b. Liquid Ordered Liquid Disordered

  31. Measuring Rate of Phospholipid Mobility

  32. Membrane Lipid Movement over 56 msec EOC Problem 6 involves temperature effects on lateral diffusion in membranes.

  33. Some Membrane Proteins Have Cytoskeleton Restricted Movement

  34. Atomic Force Microscopy

  35. AFM Aquaporin from E. coli – Outside View

  36. Rafts and GPI-linked Proteins Rafts and Sea

  37. AFM Detects “Rafts” of Sphingolipids + Cholesterol

  38. Hierarchy of raft-based heterogeneity in cell membranes D Lingwood, K Simons Science 2010;327:46-50 Published by AAAS

  39. Integral Membrane Proteins Involved in Cell-Cell Communication

  40. Membrane Fusion Events,An Overview To do this, proteins have to get two membranes very close together so they touch.

  41. Caveolin Dimers form Caveloa

  42. Three Models for Protein-Induced Curvature

  43. Types of Endocytosis

  44. Influenzia Virus Must “Uncoat” in Cytoplasm

  45. Things to Know and Do Before Class The major and minor membrane phospholipids. Transmembrane protein structures and how they are held into the membrane. Peripheral membrane proteins and how they are attached to the membrane. Membrane temperature driven transitions. What AFM tells us about membrane structure. Membrane fusions + formation of endosomes. EOC Problems: 3, 5, 6 (Hint need to calc SDS mole wt 288 Daltons)

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