1. Chapter 8 Membrane Structure and Function

2. Plasma Membrane

3. Membrane Composition u Question: How are the materials arranged?

4. Lipid Bilayer u Phospholipids u Hydrophilic heads u Hydrophobic tails

5. Membrane Models

6. Davson-Danielli Model 1935 u Lipid bilayer. u Proteins coat the surfaces. u Sometimes called the “sandwich” model.

7. Evidence u Biochemical work. u TEM pictures show the membrane as a double line.

9. Problems u Not all membranes in a cell were the same. u How could the proteins stay in place? u Result - the model was questioned and tested by scientific process.

10. Fluid Mosaic Model 1972 u New model to fit the new evidence with membranes. u Example of “Science as a Process”.

11. Fluid Mosaic Model

12. “Fluid”

13. Ways to keep the membrane “fluid”

15. “Mosaic”

16. Evidence u TEM pictures of fractured membranes. u Cell fusion studies. u Tagging of membrane proteins by antibodies.

20. Protein Function in Membranes

22. Types of Membrane Proteins u Integral – u Peripheral -

24. Question? u How do the integral proteins stick to the membrane?

25. Hydrophilic Amino Acids Hydrophobic Amino Acids Hydrophilic Amino Acids

26. Membranes are Bifacial

27. Carbohydrates

28. Membrane Carbohydrates

29. Question u How do materials get across a cell's membrane?

30. Problems u Lipid bilayer is hydrophobic. Hydrophilic materials don't cross easily. u Large molecules don't cross easily. Too big to get through the membrane.

31. Mechanisms 1. 2.

32. Passive Transport

33. Types of Passive Transport 1. 2. 3.

34. Diffusion

36. Equilibrium

37. Factors that Effect Diffusion 1.

38. Osmosis

39. Tonicity

41. Isotonic

42. Hypotonic

43. Hypertonic u.u.

44. Facilitated Diffusion

46. Aquaporins u Newly found channels for osmosis. GFP labeled Aquaporins

47. Active Transport

48. Types of Active Transport 1.

49. Carrier-Mediated Transport

50. Examples 1.

52. Na + - K + pump

53. Electrogenic or H + pumps u.u.

55. Cotransport

57. Exocytosis

58. Endocytosis u.u.

59. Types 1.

60. Carbohydrates

61. Forming vesicles

63. Summary u Know membrane structure. u Be able to discuss the various methods by which cells move materials through membranes. u Be able to solve problems in osmosis.