1. Membrane Chapter 7

2. Cell membrane

4. Cell Membrane Plasma membrane Selective permeability Surrounds all living cells 2 molecules thick.

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6. Plasma Membrane Interacts with environment Exchanges information Manages movement in & out of cell

7. Fluid mosaic model Revised in 1972 by Singer & Nicolson Globular proteins imbedded in the membrane Not surrounding the lipid layer Proteins “float” in the membrane like boats in a pond.

8. Plasma membrane Lipid membrane (phospholipids) Protein passageways Allow water-soluble substances to pass

9. Membrane Structure 1. Phospholipid layer 2. Cholesterol 3. Transmembrane proteins 4. Interior protein network 5. Cell surface markers

10. Membrane structure

11. Triglycerides Water insoluble Non-polar

12. Phospholipid Glycerol (3 carbon alcohol) 2 fatty acids Phosphate attached to 3 rd carbon

15. Phospholipid bilayer Orients polar head toward water molecules Non-polar tail away from water. Non-polar barrier to water soluble molecules

16. Phospholipid bilayer Hydrophobic interactions hold membrane together Phospholipids & unanchored proteins move freely within the membrane

18. Cholesterol Located between lipids Increases or decreases fluidity Depends on temperature.

19. Cholesterol

20. Structures of membrane proteins 1. Peripheral proteins Attached to the surface membrane 2. Integral proteins Extend through the membrane Transmembrane proteins Partway

21. Structures of membrane proteins Non-polar section of protein Contact with the non-polar interior (hydrophobic) Polar section of the protein Extends out of membrane

22. Transmembrane proteins 1. Single-pass anchors 2. Multiple-pass channels and carriers 3. Pores Aquaporins

26. Functions of membrane proteins 1. Transport Allow specific substances to enter or leave 2. Enzymes Carry out reactions on interior surface 3. Cell surface receptors Sensitive to chemical messages

27. Functions of membrane proteins 4. Cell surface identity markers Cell recognition between cells Glycoproteins 5. Cell adhesion proteins Proteins stick to each other Temporary or more permanently 6. Attachments to the cytoskeleton

28. Membrane Proteins

29. Membrane structure

30. Membrane formation Proteins & lipids made in ER Processed in Gogi apparatus Vesicles Fuse with membrane Correct orientation

31. Movement across the membrane 1. Passive transport 2. Bulk transport 3. Active transport

32. Passive transport Diffusion High concentration to areas of lower concentration Concentrations are the same in all regions

33. Passive transport Two conditions determine the direction of the flow of ions 1. Relative concentration of the ion on each side of the membrane 2. The voltage across the membrane

34. Diffusion

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36. Osmosis Net movement of water across a membrane Moves towards an area of lower water concentration Or higher solute concentration Passive transport of water

37. Osmosis Osmoregulation: Control of water balance

38. Osmosis Hyperosmostic Solution with higher concentration of solute Has less water Hypoosmostic Solution with the lower concentration of solute Has more water Isosmostic Solutions have equal concentration of solutes

39. Solutions Solute Substance being dissolved Solvent Substance doing the dissolving

40. Solutions Hypertonic: Solution with higher concentration of solute Hypotonic: Solution with lower concentration of solute Isotonic Solutions with equal solute concentrations

43. Facilitated diffusion Carriers transport Ions, aa or sugars across the membrane Specific for type of solute Moves from high concentration to low The carrier facilitates the process

45. Examples RBC diffusion of the bicarbonate ion RBC diffusion of glucose

46. Facilitated diffusion 1. It is specific 2. It is passive 3. It saturate Carriers are saturated Transport rate cannot increase Despite the concentration gradient

47. Bulk transport Endocytosis Membrane envelops food particles 1. Phagocytosis 2. Pinocytosis 3. Receptor-mediated endocytosis

48. Bulk transport Phagocytosis: The cell engulfs particles Pinocytosis: The cell engulfs liquid Receptor-mediated: Transported molecules bind specific receptors in the plasma membrane

49. Phagocytosis

50. Pinocytosis

51. Receptor-mediated

52. Exocytosis The reverse of endocytosis Discharge of materials from the cell Secretion of many hormones, neurotransmitters, digestive enzymes and other substances

53. Active transport Movement of substances against or up the concentration gradient Low concentration to high Requires energy. Requires the use of ATP. Cell takes up substances into cytoplasm that are already hypertonic to the extracellular fluid.

54. Sodium-potassium pump Protein transports Na and K ions across the membrane. Every cycle transports 3 Na ions out Exchange for 2 K ions into the cell Against concentration gradients.

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57. Coupled transport Molecule moves up its concentration gradient Uses the drive from another substance moving down its concentration gradient. Na ions and glucose

58. Fig. 7-19 Proton pump – – – – – – + + + + + + ATP H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Diffusion of H + Sucrose-H + cotransporter Sucrose