CELL STRUCTURE & FUNCTION

Transcription

1 CELL STRUCTURE & FUNCTION Professor Andrea Garrison Biology 3A Illustrations 2010, 2013 Pearson Education, Inc.

2 Cells Most basic unit of living system Arise by cell division from existing cell Make up all living organisms All living things composed of one or more cells & cell products What is Life? 2

3 Basic cell structure Cytoplasm 80% water, organelles Nucleus Contains genetic material; controls cell activities Cell membrane Separates cell from environment and regulates passage in/out of cell Cell Structure and Function 3

4 How tiny are cells, anyway? Cell Structure and Function 4

5 How tiny are cells, anyway? Very, very tiny Cell Structure and Function 5

6 Resolution of microscope lenses Cell Structure and Function 6

7 Electron Microscope Used to see things smaller than 0.1 mm (= 100 μm) Uses beam of electrons to see structures Scanning EM used to study surface of object Transmission EM used to internal structure Cell Structure and Function 7

8 Light microscope SEM TEM Cell Structure and Function 8

9 Categories of Cells Based on how they feed Autotrophs vs. Heterotrophs Based on cell structure Prokaryotes vs. Eukaryotes Cell Structure and Function 9

10 Categories of Cells Autotrophs make their own food Heterotrophs eat another organism Cell Structure and Funciton; 2013, Pearson Education, Inc. 10

11 Categories of Cells Prokaryotes lack organelles Eukaryotes have organelles Cell Structure and Function 11

12 Organelles Internal membrane-bound structures For example, nucleus & chloroplasts Cell Structure and Function 12

13 Organelles Internal membrane-bound structures For example, nucleus & chloroplasts Perform specific functions Nucleus contains DNA, transcribes genetic code into messages that control cell activities Chloroplasts site of photosynthesis Cell Structure and Function 13

14 Eukaryote--organelles Cell Structure and Function 14

15 Eukaryotic Cell Structure Variety of organelles present Cell structure related to cell function Not all organelles present in all cell types Abundance of organelles may vary Cell Structure and Function 15

16 Plant vs. Animal Cells Plant cells Cell wall Chloroplasts for P/S Central vacuole None None Animal cells None None None Lysosomes Centrioles to assist with cell division Cell Structure and Function 16

17 Plant vs. Animal Cells Cell Structure and Function 17

18 Plant vs. Animal Cells Cell Structure and Function 18

19 Nucleus Functions: Holds genetic material (DNA) Controls cell activities Pores allow chemical communication with cytoplasm Cell Structure and Function 19

20 Vacuoles Sacs pinched off from internal membrane or plasma membrane Variety of types with different functions Contractile vacuoles in Protista Central vacuole in plants Cell Structure and Function 20

21 Vacuoles Contractile vacuole Absorbs excess water in cytoplasm Contracts to expel excess water Cell Structure and Function 21

22 Vacuoles Central vacuole Storage Water Nutrients Wastes Toxins Pigments Cell Structure and Function 22

23 Lysosomes Sacs pinched off from Golgi membrane Contain digestive enzymes Intracellular digestion Food vacuoles to digest food Damaged organelles Cell destruction after death Cell Structure and Function 23

24 Lysosomes Cell Structure and Function 24

25 Organelles associated with energy Plastids (incl. chloroplasts) and mitochondria Provide cellular energy Contain their own DNA Feature not found in other organelles Encodes some of their proteins Still require nuclear DNA for full function Considered evidence that these organelles evolved from free-living prokaryotes which were engulfed and became endosymbionts, then eventually became obligate Cell Structure and Function 25

26 Organelles associated with energy Chloroplasts Found in photosynthetic cells plants and some protistans Site of P/S Large amount of membrane Cell Structure and Function 26

27 Other Plastids Store pigments or P/S products Ex: chromoplasts Synthesize and store pigments Flowers, ripening fruits, aging leaves Ex: amyloplasts synthesize, store and breakdown starch Amyloplasts in potato cells Cell Structure and Function; photo by Mnolf; 27

28 Organelles associated with energy Mitochondria Found in all eukaryotes Site of ATP production Large amount of membrane Cell Structure and Function 28

29 Non-membrane bound structures Found in prokaryotes or eukaryotes May or may not be found in all cells Cell Structure and Function 29

30 Non-membrane bound structures Cytoskeleton Network of fibers Function Support Movement Cell Structure and Function 30

31 Non-membrane bound structures Cytoskeleton Support Maintains cell shape Holds organelles in place Cell Structure and Function 31

32 Non-membrane bound structures Cytoskeleton Movement Network of fibers constantly dissolving and reforming in new arrangements Allows cell to change shapes Allows chromosomes to move apart during cell division Cell Structure and Function 32

33 Non-membrane bound structures Centrioles Occur in pairs Act as anchor to pull chromosomes apart during cell division Not found in plant cells centrioles Cell Structure and Function 33

34 Non-membrane bound structures Flagella & Cilia Hair-like structures that aid in movement Move cells through liquid Create currents past non-moving cells Cell Structure and Function 34

35 Non-membrane bound structures Flagella Long whipping tails Usually 1-3 per cell Propel cell forward Found in many protists Found in human sperm Cell Structure and Function 35

36 Non-membrane bound structures Cilia Short hair-like structures Usually many on cell surface Beat in synchrony Found in many protists Found in human tissues Cell Structure and Function 36

37 Non-membrane bound structures Cell Structure and Function 37

38 Non-membrane bound structures Cell Wall Found in variety of cells Bacteria Protistans Plants Fungus Protective structure outside plasma membrane Porous to water, salts Cell wall Cell Structure and Function 38

39 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 39

40 Plasma Membranes Cell cytoplasm about 80% water Extracellular fluid (outside cell) about 80% water Water has a drastic effect on cell structure Cell Membranes 40

41 Water and oil don t mix Cell Membranes 41

42 Properties of water related charge Based on what you know about how water reacts with fat and oil molecules, what type of molecules would you expect your cell membranes to be made of? Cell Membranes 42

43 Fluid Mosaic Model of Plasma Plasma membrane a mosaic Phospholipids Proteins Fluid structure Molecules move around freely in the membrane Membrane 43

44 Fluid Mosaic Model of Plasma Phospholipids Form bilayer Foundation of membrane Membrane 44

45 Fluid Mosaic Model of Plasma Membrane Phospholipids Hydrophilic head charged water-loving attracted to water + Hydrophobic tails No charge water-fearing repel water 45

46 Fluid Mosaic Model of Plasma Phospholipids Hydrophilic heads Contact water inside and outside cell Hydrophobic tails No contact with water Membrane 46

47 Fluid Mosaic Model of Plasma Phospholipids Prevent most substances from crossing membrane Only very small molecules with little or no charge can get through Membrane 47

48 Proteins Fluid Mosaic Model of Plasma Allow specific substances to get through (based on shape) Hydrophilic portions Contact water Hydrophobic portions No contact with water Membrane 48

49 Membrane Permeability Let s look at the plasma membrane s regulation of transport in/out of cell Cell Membranes 49

50 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 50

51 Diffusion (Passive Transport) Requires no energy on part of cell; tends toward equilibrium Cell Membranes 51

52 Membrane Permeability Diffusion of oxygen and carbon dioxide are not a problem in normal situations Diffusion of water can be a problem Cell Membranes 52

53 Osmosis Special case of diffusion Diffusion of water (high concentration water low concentration water) across selectively permeable membrane Cell Membranes 53

54 Osmosis To understand osmosis, must understand solutions SOLUTION = SOLUTE + SOLVENT Dissolved + water particles Concentration of solution = % solute Cell Membranes 54

55 Osmosis Concentration of solution considers %solute Osmosis considers %water (solvent) 90% salt solution = 90% salt and 10% water Cell Membranes 55

56 Osmosis Which has greater salt? 90% salt or 50% salt? Cell Membranes 56

57 Osmosis Which has greater salt? 90% salt or 50% salt? Cell Membranes 57

58 Osmosis Which has greater salt? 90% salt or 50% salt? Which has greater water? 90% salt or 50% salt? Cell Membranes 58

59 Osmosis Which has greater salt? 90% salt or 50% salt? Which has greater water? 90% salt or 50% salt? Cell Membranes 59

60 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 60

61 Osmosis Which side has more water? What direction will water move? Cell Membranes 61

62 Osmosis Which side has more water? What direction will water move? Cell Membranes 62

63 Osmosis Water moves from side where water is greater to side where water is less (low salt to high salt) Cell Membranes 63

64 Osmosis Cell Membranes 64

65 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 65

66 Osmosis Isotonic solution surrounds cell No net movement of water Cell remains healthy 0.9% salt 0.9 % salt Cell Membranes 66

67 Osmosis Hypotonic solution surrounds cell Water enters cell Cell swells/bursts 0.1% salt 0.% salt 0.9% salt Cell Membranes 67

68 Osmosis Hypertonic solution surrounds cell Water leaves cell Cell shrivels 10 % salt 0.9% salt Cell Membranes 68

69 Osmosis Plant and animal cells affected by osmosis Cell Membranes 69

70 Osmosis Cell Membranes 70

71 Plant Turgor Effects of Osmosis Cell Membranes 71

72 Membrane Permeability Regulated substances Move across membrane via transport proteins Facilitated diffusion Active transport 72

73 Summary of Transport Mechanisms Cell Membranes 73

74 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 74

75 Bulk transport Endocytosis Exocytosis Membrane Transport Cell Membranes 75

76 Bulk transport Endocytosis Membrane Transport Substance moved into cell via pinching of membrane into vacuole 76

77 Bulk transport Endocytosis Membrane Transport Substance moved into cell via pinching of membrane into vacuole Phagocytosis vs. pinocytosis 77

78 Membrane Transport Bulk transport Exocytosis Substance moved out of cell via fusion of vesicle with membrane 78