Chapter 5. The Working Cell. Lectures by Chris C. Romero, updated by Edward J. Zalisko

Transcription

1 Chapter 5 The Working Cell PowerPoint Lectures for Campbell Essential Biology, Fourth Edition Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition Eric Simon, Jane Reece, and Jean Dickey Lectures by Chris C. Romero, updated by Edward J. Zalisko 2010 Pearson Education, Inc. 0

2 Biology and Society: Natural Nanotechnology Cells control their chemical environment using Energy Enzymes The plasma membrane Cell-based nanotechnology may be used to power microscopic robots Pearson Education, Inc.

3 Figure 5.00

4 SOME BASIC ENERGY CONCEPTS Energy makes the world go around. But what is energy? 2010 Pearson Education, Inc.

5 Conservation of Energy Energy is defined as the capacity to perform work. Kinetic energy is the energy of motion. Potential energy is stored energy. Animation: Energy Concepts 2010 Pearson Education, Inc.

6 On the platform, the diver has more potential energy. Climbing the steps converts kinetic energy of muscle movement to potential energy. Diving converts potential energy to kinetic energy. In the water, the diver has less potential energy. Figure 5.1

7 Machines and organisms can transform kinetic energy to potential energy and vice versa. In all such energy transformations, total energy is conserved. Energy cannot be created or destroyed. This is the principle of conservation of energy Pearson Education, Inc.

8 Entropy Every energy conversion releases some randomized energy in the form of heat. Heat is a Type of kinetic energy Product of all energy conversions 2010 Pearson Education, Inc.

9 Scientists use the term entropy as a measure of disorder, or randomness. All energy conversions increase the entropy of the universe Pearson Education, Inc.

10 Chemical Energy Molecules store varying amounts of potential energy in the arrangement of their atoms. Organic compounds are relatively rich in such chemical energy Pearson Education, Inc.

11 Living cells and automobile engines use the same basic process to make chemical energy do work Pearson Education, Inc.

12 Fuel rich in chemical energy Energy conversion Waste products poor in chemical energy Heat energy Gasoline + Combustion Kinetic energy of movement Oxygen Carbon dioxide + Water Energy conversion in a car Heat energy Cellular respiration Food + Oxygen ATP Energy for cellular work Carbon dioxide + Water Energy conversion in a cell Figure 5.2

13 Cellular respiration is the energy-releasing chemical breakdown of fuel molecules that provides energy for cells to do work. Humans convert about 40% of the energy in food to useful work, such as the contraction of muscles Pearson Education, Inc.

14 Food Calories A calorie is the amount of energy that raises the temperature of one gram of water by 1 degree Celsius. Food Calories are kilocalories, equal to 1,000 calories Pearson Education, Inc.

15 Food Food Calories Cheeseburger 295 Spaghetti with sauce (1 cup) 241 Baked potato (plain, with skin) 220 Activity Food Calories consumed per hour by a 150-pound person* Running (7min/mi) 979 Dancing (fast) 510 Bicycling (10 mph) 490 Fried chicken (drumstick) 193 Swimming (2 mph) Bean burrito 189 Walking (3 mph) Pizza with pepperoni (1 slice) 181 Dancing (slow) Peanuts (1 ounce) 166 Playing the piano 73 Driving a car 61 Apple Garden salad (2 cups) Popcorn (plain, 1 cup) 31 Broccoli (1 cup) 25 (a) Food Calories (kilocalories) in various foods Sitting (writing) *Not including energy necessary for basic functions, such as breathing and heartbeat (b) Food Calories (kilocalories) we burn in various activities Figure 5.3

16 Food Food Calories Cheeseburger 295 Spaghetti with sauce (1 cup) 241 Baked potato (plain, with skin) 220 Fried chicken (drumstick) 193 Bean burrito 189 Pizza with pepperoni (1 slice) 181 Peanuts (1 ounce) 166 Apple Garden salad (2 cups) Popcorn (plain, 1 cup) 31 Broccoli (1 cup) 25 (a) Food Calories (kilocalories) in various foods Figure 5.3a

17 Activity Food Calories consumed per hour by a 150-pound person* Running (7min/mi) 979 Dancing (fast) 510 Bicycling (10 mph) 490 Swimming (2 mph) 408 Walking (3 mph) 245 Dancing (slow) 204 Playing the piano 73 Driving a car 61 Sitting (writing) 28 *Not including energy necessary for basic functions, such as breathing and heartbeat (b) Food Calories (kilocalories) we burn in various activities Figure 5.3b

18 The energy of calories in food is burned off by many activities Pearson Education, Inc.

19 ATP AND CELLULAR WORK Chemical energy is Released by the breakdown of organic molecules during cellular respiration Used to generate molecules of ATP 2010 Pearson Education, Inc.

20 ATP Acts like an energy shuttle Stores energy obtained from food Releases it later as needed 2010 Pearson Education, Inc.

21 The Structure of ATP ATP (adenosine triphosphate) Consists of adenosine plus a tail of three phosphate groups Is broken down to ADP and a phosphate group, releasing energy Blast Animation: Structure of ATP 2010 Pearson Education, Inc.

22 Energy Triphosphate Adenosine P ATP P P Diphosphate Adenosine ADP P P P Phosphate (transferred to another molecule) Figure 5.4

23 Phosphate Transfer ATP energizes other molecules by transferring phosphate groups. This energy helps cells perform Mechanical work Transport work Chemical work 2010 Pearson Education, Inc.

24 Motor protein ATP ADP P ADP P ADP P ADP P Protein moved (a) Motor protein performing mechanical work Transport Solute protein P P ATP Solute transported (b) Transport protein performing transport work P ATP X P X Y Y Reactants Product made (c) Chemical reactants performing chemical work Figure 5.5

25 Motor protein ATP ADP P ADP P Protein moved (a) Motor protein performing mechanical work Figure 5.5a

26 Transport Solute protein P P ATP ADP P Solute transported (b) Transport protein performing transport work Figure 5.5b

27 P ATP X P X Y ADP P Y Reactants Product made (c) Chemical reactants performing chemical work Figure 5.5c

28 The ATP Cycle Cellular work spends ATP. ATP is recycled from ADP and a phosphate group through cellular respiration. A working muscle cell spends and recycles about 10 million ATP molecules per second. Blast Animation: ATP/ADP Cycle 2010 Pearson Education, Inc.

29 ATP Cellular respiration: chemical energy harvested from fuel molecules Energy for cellular work ADP P Figure 5.6

30 ENZYMES Metabolism is the total of all chemical reactions in an organism. Most metabolic reactions require the assistance of enzymes, proteins that speed up chemical reactions Pearson Education, Inc.

31 Activation Energy Activation energy Activates the reactants Triggers a chemical reaction Enzymes lower the activation energy for chemical reactions. Blast Animation: How Enzymes Work: Activation Energy 2010 Pearson Education, Inc.

32 Activation energy barrier Reactant Energy level Energy level Enzyme Reactant Products (a) Without enzyme Activation energy barrier reduced by enzyme Products (b) With enzyme Figure 5.7

33 Activation energy barrier Energy level Reactant Products (a) Without enzyme Figure 5.7a

34 Enzyme Activation energy barrier reduced by enzyme Energy level Reactant Products (b) With enzyme Figure 5.7b

35 The Process of Science: Can Enzymes Be Engineered? Observation: Genetic sequences suggest that many of our genes were formed through a type of molecular evolution. Question: Can laboratory methods form new enzymes through artificial selection? Hypothesis: An artificial process could modify the gene that codes for lactase into a new gene with a new function Pearson Education, Inc.

36 Experiment: Many copies of the lactase gene were randomly mutated and tested for new activities. Results: Directed evolution produced a new enzyme with a novel function Pearson Education, Inc.

37 Gene for lactase Gene duplicated and mutated at random Mutated genes (mutations shown in orange) Mutated genes screened by testing new enzymes Genes coding for enzymes that show new activity Genes duplicated and mutated at random Genes coding for enzymes that do not show new activity Ribbon model showing the polypeptide chains of the enzyme lactase Mutated genes screened by testing new enzymes After seven rounds, some genes code for enzymes that can efficiently perform new activity. Figure 5.8

38 Gene for lactase Gene duplicated and mutated at random Mutated genes (mutations shown in orange) Mutated genes screened by testing new enzymes Genes coding for enzymes that show new activity Genes coding for enzymes that do not show new activity Genes duplicated and mutated at random Mutated genes screened by testing new enzymes After seven rounds, some genes code for enzymes that can efficiently perform new activity. Figure 5.8a

39 Ribbon model showing the polypeptide chains of the enzyme lactase Figure 5.8b

40 Induced Fit Every enzyme is very selective, catalyzing a specific reaction Pearson Education, Inc.

41 Each enzyme recognizes a substrate, a specific reactant molecule. The active site fits to the substrate, and the enzyme changes shape slightly. This interaction is called induced fit Pearson Education, Inc.

42 Enzymes can function over and over again, a key characteristic of enzymes. Animation: How Enzymes Work 2010 Pearson Education, Inc.

43 Active site Sucrase can accept a molecule of its substrate. Enzyme (sucrase) Figure 5.9-1

44 Substrate (sucrose) Active site Sucrase can accept a molecule of its substrate. Substrate binds to the enzyme. Enzyme (sucrase) Figure 5.9-2

45 Substrate (sucrose) Active site Sucrase can accept a molecule of its substrate. Substrate binds to the enzyme. Enzyme (sucrase) H2O The enzyme catalyzes the chemical reaction. Figure 5.9-3

46 Substrate (sucrose) Active site Sucrase can accept a molecule of its substrate. Substrate binds to the enzyme. Enzyme (sucrase) Fructose H2O Glucose The products are released. The enzyme catalyzes the chemical reaction. Figure 5.9-4

47 Enzyme Inhibitors Enzyme inhibitors can prevent metabolic reactions by binding to the active site. Blast Animation: Enzyme Regulation: Competitive Inhibition 2010 Pearson Education, Inc.

48 (a) Enzyme and substrate binding normally Substrate Active site (b) Enzyme inhibition by a substrate imposter Enzyme Substrate Inhibitor Active site Enzyme (c) Enzyme inhibition by a molecule that causes the active site to change shape Active site Substrate Inhibitor Enzyme Figure 5.10

49 Substrate Active site Enzyme (a) Enzyme and substrate binding normally Figure 5.10a

50 Inhibitor Substrate Active site Enzyme (b) Enzyme inhibition by a substrate imposter Figure 5.10b

51 Substrate Active site Inhibitor Enzyme (c) Enzyme inhibition by a molecule that causes the active site to change shape Figure 5.10c

52 Other enzyme inhibitors Bind at a remote site Change the enzyme s shape Prevent the enzyme from binding to its substrate 2010 Pearson Education, Inc.

53 Some products of a reaction may inhibit the enzyme required for its production. This is called feedback regulation. It prevents the cell from wasting resources. Many antibiotics work by inhibiting enzymes of disease-causing bacteria Pearson Education, Inc.

54 MEMBRANE FUNCTION Working cells must control the flow of materials to and from the environment. Membrane proteins perform many functions. Transport proteins Are located in membranes Regulate the passage of materials into and out of the cell Animation: Membrane Selectivity 2010 Pearson Education, Inc.

55 Enzymatic activity Cytoplasm Fibers of extracellular matrix Cell signaling Attachment to the cytoskeleton and extracellular matrix Cytoplasm Cytoskeleton Transport Intercellular joining Cell-cell recognition Figure 5.11

56 Passive Transport: Diffusion across Membranes Molecules contain heat energy that causes them to vibrate and wander randomly. Diffusion is the tendency for molecules of any substance to spread out into the available space Pearson Education, Inc.

57 Passive transport is the diffusion of a substance across a membrane without the input of energy. Diffusion is an example of passive transport. Substances diffuse down their concentration gradient, a region in which the substance s density changes. Blast Animation: Diffusion Animation: Diffusion Blast Animation: Passive Diffusion Across a Membrane 2010 Pearson Education, Inc.

58 Molecules of dye Net diffusion Membrane Net diffusion Equilibrium (a) Passive transport of one type of molecule Net diffusion Net diffusion Net diffusion Net diffusion (b) Passive transport of two types of molecules Equilibrium Equilibrium Figure 5.12

59 Molecules of dye Net diffusion Membrane Net diffusion Equilibrium (a) Passive transport of one type of molecule Figure 5.12a

60 Net diffusion Net diffusion Net diffusion Net diffusion Equilibrium Equilibrium (b) Passive transport of two types of molecules Figure 5.12b

61 Some substances do not cross membranes spontaneously. These substances can be transported via facilitated diffusion. Specific transport proteins act as selective corridors. No energy input is needed Pearson Education, Inc.

62 Osmosis and Water Balance The diffusion of water across a selectively permeable membrane is osmosis. Animation: Osmosis 2010 Pearson Education, Inc.

63 Hypotonic solution Hypertonic solution Sugar molecule Selectively permeable membrane Osmosis Figure

64 Hypotonic solution Hypertonic solution Isotonic solutions Osmosis Sugar molecule Selectively permeable membrane Osmosis Figure

65 A hypertonic solution has a higher concentration of solute. A hypotonic solution has a lower concentration of solute. An isotonic solution has an equal concentration of solute Pearson Education, Inc.

66 Water Balance in Animal Cells Osmoregulation is the control of water balance within a cell or organism. Most animal cells require an isotonic environment Pearson Education, Inc.

67 Water Balance in Plant Cells Plant have rigid cell walls. Plant cells require a hypotonic environment, which keeps these walled cells turgid. Video: Plasmolysis 2010 Pearson Education, Inc.

68 Animal cell H2O H2O H2O Normal Lysing H 2O Flaccid (wilts) (a) Isotonic solution Shriveled Plasma membrane Plant cell H2O H2O H2O Turgid (b) Hypotonic solution H 2O Shriveled (c) Hypertonic solution Figure 5.14

69 Animal cell H2O H2O Normal Plant cell H 2O H2O Flaccid (wilts) (a) Isotonic solution Figure 5.14a

70 H2O Lysing H2O Turgid (b) Hypotonic solution Figure 5.14b

71 H 2O Shriveled Plasma membrane H 2O Shriveled (c) Hypertonic solution Figure 5.14c

72 As a plant cell loses water, It shrivels. Its plasma membrane may pull away from the cell wall in the process of plasmolysis, which usually kills the cell. Video: Turgid Elodea 2010 Pearson Education, Inc.

73 Figure 5.15

74 Active Transport: The Pumping of Molecules Across Membranes Active transport requires energy to move molecules across a membrane. Blast Animation: Active Transport: Sodium-Potassium Pump Animation: Active Transport 2010 Pearson Education, Inc.

75 Lower solute concentration Solute ATP Higher solute concentration Figure

76 Lower solute concentration Solute ATP Higher solute concentration Figure

77 Exocytosis and Endocytosis: Traffic of Large Molecules Exocytosis is the secretion of large molecules within vesicles. Blast Animation: Endocytosis and Exocytosis Animation: Exocytosis and Endocytosis Introduction Animation: Exocytosis 2010 Pearson Education, Inc.

78 Outside of cell Plasma membrane Cytoplasm Figure 5.17

79 Endocytosis takes material into a cell within vesicles that bud inward from the plasma membrane. Animation: Phagocytosis Animation: Pinocytosis Animation: Receptor-Mediated Endocytosis 2010 Pearson Education, Inc.

80 Figure 5.18

81 There are three types of endocytosis: Phagocytosis ( cellular eating ); a cell engulfs a particle and packages it within a food vacuole Pinocytosis ( cellular drinking ); a cell gulps droplets of fluid by forming tiny vesicles Receptor-mediated endocytosis; a cell takes in very specific molecules 2010 Pearson Education, Inc.

82 The Role of Membranes in Cell Signaling The plasma membrane helps convey signals between Cells Cells and their environment 2010 Pearson Education, Inc.

83 Receptors on a cell surface trigger signal transduction pathways that Relay the signal Convert it to chemical forms that can function within the cell Animation: Overview of Cell Signaling Animation: Signal Transduction Pathways 2010 Pearson Education, Inc.

84 Outside of cell Receptor protein Reception Cytoplasm Transduction Proteins of signal transduction pathway Epinephrine (adrenaline) from adrenal glands Response Hydrolysis of glycogen releases glucose for energy Plasma membrane Figure 5.19

85 Outside of cell Reception Receptor protein Cytoplasm Transduction Proteins of signal transduction pathway Epinephrine (adrenaline) from adrenal glands Response Hydrolysis of glycogen releases glucose for energy Plasma membrane Figure 5.19a

86 Evolution Connection: The Origin of Membranes Phospholipids Are key ingredients of membranes Were probably among the first organic compounds that formed before life emerged Self-assemble into simple membranes 2010 Pearson Education, Inc.

87 Figure 5.20

88 Energy for cellular work Adenosine P P P ATP cycle Adenosine P ATP ADP Adenosine triphosphate Adenosine diphosphate Energy from organic fuel P P Phosphate Figure 5.UN01

89 Activation energy Enzyme added Reactant Reactant Products Products Figure 5.UN02

90 MEMBRANE TRANSPORT Passive Transport (requires no energy) Active Transport (requires energy) Lower solute concentration Higher solute concentration Lower water concentration (higher solute concentration) Solute Water Solute Solute Diffusion Facilitated diffusion Osmosis Higher water concentration Higher solute concentration (lower solute concentration) Solute ATP Lower solute concentration Figure 5.UN03

91 Exocytosis Endocytosis Figure 5.UN04