CELL MEMBRANES. Professor Andrea Garrison Biology 11 Illustrations 2010 Pearson Education, Inc. unless otherwise noted

Transcription

1 CELL MEMBRANES Professor Andrea Garrison Biology 11 Illustrations 2010 Pearson Education, Inc. unless otherwise noted

2 Plasma Membranes Plasma membrane = external cell membrane Surrounds cell Separates cell s internal environment from external environment Regulates passage of molecules in/out of cell Allows homeostasis Cell Membranes 2

3 Plasma Membranes Cell cytoplasm about 80% water Extracellular fluid (outside cell) about 80% water Water has a drastic effect on cell structure Water very unique molecule Cell Membranes 3

4 Water (H 2 O) 2 hydrogen atoms and 1 oxygen atom Bond represents sharing of 2 electrons Cell Membranes 4

5 Water (H 2 O) H 2 O is polar molecule Electrons spend more time around oxygen Molecule slightly charged on each end Cell Membranes 5

6 Water (H 2 O) Water forms hydrogen bonds Opposite charges on different ends of molecules attract each other H-bonds are very weak Break easily Cell Membranes 6

7 Properties of water related to H-bonds High surface tension H-bonds hold water molecules together Takes significant weight to break the bonds Raft Spider, Europe, 3 legspan Cell Membranes 7

8 Properties of water related to H-bonds High surface tension H-bonds hold water molecules together Evaporation from leaves acts like sucking on straw to pull water up Cell Membranes 8

9 Properties of water related to H-bonds High heat capacity Heat makes molecules vibrate Temperature is a measure of the amount of vibration Some energy has to break H-bonds before they vibrate Water absorbs a lot of energy before temperature increases Cell Membranes 2012 Amy Garrison 9

10 Properties of water related to H-bonds High heat capacity Water moderates climate Cell Membranes 2012 Amy Garrison 10

11 Properties of water related to H-bonds High heat capacity Water moderates climate Water moderates body temperature Water cools by evaporative cooling Cell Membranes 11

12 Properties of water related to H-bonds Ice floats Liquid water is dense H-bonds constantly break and reform Solid water is less dense H-bonds last longer Arrangement more spacious Cell Membranes 12

13 Properties of water related charge Universal solvent Charges on water molecule allow it to dissolve many substances Charges attract opposite charges on other molecules, such as Na + Cl - Cell Membranes 13

14 Properties of water related to charge Does not react with nonpolar (non-charged) molecules Oil has no charge Vinegar has water in it and is charged Cell Membranes 14

15 Properties of water related charge Based on what you know about how water reacts with charged and non-charged molecules, what type of molecules would you expect your cell membranes to be made of? Cell Membranes 15

16 Fluid Mosaic Model of Plasma Plasma membrane a mosaic Phospholipids Proteins Fluid structure Molecules move around freely in the membrane Membrane Cell Membranes 16

17 Fluid Mosaic Model of Plasma Membrane Phospholipids Form bilayer Foundation of membrane Has H 2 O Has H 2 O Cell Membranes 17

18 Fluid Mosaic Model of Plasma Membrane Phospholipids + Hydrophilic head charged water-loving attracted to water Hydrophobic tails No charge water-fearing repel water Cell Membranes 18

19 Fluid Mosaic Model of Plasma Membrane Phospholipids Hydrophilic heads Contact water inside and outside cell Hydrophobic tails No contact with water Has H 2 O Has H 2 O Cell Membranes 19

20 Fluid Mosaic Model of Plasma Membrane Phospholipids Prevent most substances from crossing membrane Only very small molecules with little or no charge can get through Has H 2 O Has H 2 O Cell Membranes 20

21 Fluid Mosaic Model of Plasma Membrane Proteins Allow specific substances to get through (based on shape) Hydrophilic portions Contact water Hydrophobic portions No contact with water Has H 2 O Has H 2 O Cell Membranes 21

22 Fluid Mosaic Model of Plasma Has H 2 O Membrane Has H 2 O Cell Membranes 22

23 Functions of Membrane Proteins Cell Membranes 23

24 Functions of Membrane Proteins =receptor protein; Binds to molecule and causes rxn inside cell Cell Membranes 24

25 Functions of Membrane Proteins Transports molecules across membrane Cell Membranes 25

26 Functions of Membrane Proteins Recognition Cell Membranes Proteins--ID body cells and types of cells 26

27 Functions of Membrane Proteins Adhesion Cell Membranes proteins holds cells together 27

28 Membrane Permeability Let s look at the plasma membrane s regulation of transport in/out of cell? Cell Membranes 28

29 Membrane Permeability Plasma membrane freely permeable (cannot regulate): Water Oxygen Carbon dioxide These molecules move across membrane via diffusion Diffusion = movement of molecules from region of higher concentration to region of lower concentration Cell Membranes 29

30 Diffusion (Passive Transport) Requires no energy on part of cell; tends toward equilibrium Cell Membranes 30

31 Membrane Permeability Diffusion of oxygen and carbon dioxide are not a problem in normal situations Inhaled O 2 diffuses into the blood in the lungs and out of the blood into the cells of the body Waste CO 2 diffuses out of the body cells into the blood and out of the blood into the lungs to be exhaled Diffusion of water can be a problem Cell Membranes 31

32 Osmosis Special case of diffusion Diffusion of water (high concentration water low concentration water) across selectively permeable membrane Cell Membranes 32

33 Osmosis To understand osmosis, must understand solutions SOLUTION = SOLUTE + SOLVENT Dissolved + water particles Concentration of solution = % solute Cell Membranes 33

34 Osmosis Concentration of solution considers %solute Osmosis considers %water (solvent) 90% salt solution = 90% salt and 10% water Cell Membranes 34

35 Osmosis Which has greater salt? 90% salt or 50% salt? Cell Membranes 35

36 Osmosis Which has greater salt? 90% salt or 50% salt? Cell Membranes 36

37 Osmosis Which has greater salt? 90% salt or 50% salt? Which has greater water? 90% salt or 50% salt? Cell Membranes 37

38 Osmosis Which has greater salt? 90% salt or 50% salt? Which has greater water? 90% salt or 50% salt? Cell Membranes 38

39 Osmosis Which has greater salt? 90% salt or 50% salt? Which has greater water? 90% salt or 50% salt? So more salt means less water, And vice-versa Cell Membranes 39

40 Osmosis Which side has more water? What direction will water move? Cell Membranes 40

41 Osmosis Water moves from side where water is greater to side where water is less (low salt to high salt) Cell Membranes 41

42 Osmosis Cell Membranes 42

43 Osmosis Comparing a cell to the surrounding solution Isotonic solution has equal solute to cell 0.9% salt solution surrounds 0.9% cell Hypotonic solution has less solute than cell 0.1% salt solution surrounds 0.9% cell Hypertonic solution has more solute than cell 10% salt solution surrounds 0.9% cell Cell Membranes 43

44 Osmosis Isotonic solution surrounds cell No net movement of water Cell remains healthy 0.9% salt 0.9% salt Cell Membranes 44

45 Osmosis Hypotonic solution surrounds cell Water enters cell Cell swells/bursts 0.1% salt 0.% salt 0.9% salt Cell Membranes 45

46 Osmosis Hypertonic solution surrounds cell Water leaves cell Cell shrivels 10% salt 0.9% salt Cell Membranes 46

47 Osmosis Plant and animal cells affected by osmosis Cell Membranes 47

48 Osmosis Cell Membranes 48

49 Plant Turgor Effects of Osmosis Cell Membranes 49

50 Membrane Permeability Regulated substances -- Move across membrane via transport proteins Cell Membranes 50

51 Membrane Permeability Regulated substances -- Move across membrane via transport proteins Facilitated diffusion Active transport Cell Membranes 51

52 Membrane Permeability Regulated substances Facilitated diffusion Diffusion Requires help of transport protein Requires no energy (passive) Higher solute concentration Lower solute concentration Cell Membranes 52

53 Membrane Permeability Regulated substances Active transport Molecules move from lower to higher concentration Requires help of transport protein Requires energy (active) 1/3 cell s energy expended in active transport Cell Membranes 53

54 Summary of Transport Mechanisms Cell Membranes 54

55 Membrane Transport Not all substances transported one molecule at a time Bulk transport Moves molecules in bulk Moved via transport vesicle Requires energy Cell Membranes 55

56 Bulk transport Endocytosis Exocytosis Membrane Transport Cell Membranes 56

57 Bulk transport Endocytosis Membrane Transport Substance moved into cell via pinching of membrane into vacuole Outside of cell Plasma membrane Cytoplasm Cell Membranes 57

58 Bulk transport Endocytosis Membrane Transport Substance moved into cell via pinching of membrane into vacuole Phagocytosis vs. pinocytosis Outside of cell Plasma membrane Cytoplasm Cell Membranes 58

59 Membrane Transport Bulk transport Exocytosis Substance moved out of cell via fusion of vesicle with membrane Cell Membranes 59