Chapter 5. The Working Cell. Lectures by Edward J. Zalisko

Transcription

1 Chapter 5 The Working Cell PowerPoint Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition Eric J. Simon, Jean L. Dickey, and Jane B. Reece Lectures by Edward J. Zalisko

2 Biology and Society: Harnessing Cellular Structures Cells control their chemical environment using energy, enzymes, and the plasma membrane. Cell-based nanotechnology may be used to power microscopic robots.

3 Figure 5.0

4 SOME BASIC ENERGY CONCEPTS Energy makes the world go around. But what is energy?

5 Conservation of Energy Energy is defined as the capacity to cause change. Some forms of energy are used to perform work. Energy is the ability to rearrange a collection of matter.

6 Conservation of Energy Kinetic energy is the energy of motion. Potential energy is stored energy. It is energy that an object has because of its location or structure.

7 Animation: Energy Concepts Right click slide / select Play

8 Figure 5.1 Greatest potential energy Climbing converts kinetic energy to potential energy. Diving converts potential energy to kinetic energy. Least potential energy

9 Conservation of Energy 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. Energy can be converted from one form to another. This is the principle of conservation of energy.

10 Entropy Every energy conversion releases some randomized energy in the form of heat. Heat is a type of kinetic energy and product of all energy conversions.

11 Entropy Scientists use the term entropy as a measure of disorder, or randomness, in a system. All energy conversions increase the entropy of the universe.

12 Chemical Energy Molecules store varying amounts of potential energy in the arrangement of their atoms. Organic compounds are relatively rich in such chemical energy.

13 Chemical Energy Chemical energy arises from the arrangement of atoms and can be released by a chemical reaction. Living cells and automobile engines use the same basic process to make chemical energy do work.

14 Figure 5.2 Fuel rich in chemical energy Energy conversion Waste products poor in chemical energy Octane (from gasoline) Oxygen Heat energy Combustion Kinetic energy of movement Energy conversion in a car Carbon dioxide Water Heat energy Glucose (from food) Cellular respiration ATP Carbon dioxide Oxygen Energy for cellular work Energy conversion in a cell Water

15 Chemical Energy Cellular respiration is the energy-releasing chemical breakdown of fuel molecules and the storage of that energy in a form the cell can use to perform work.

16 Chemical Energy Humans convert about 34% of the energy in food to useful work, such as the contraction of muscles. About 66% of the energy released by the breakdown of fuel molecules generates body heat.

17 Food Calories A calorie is the amount of energy that can raise the temperature of one gram of water by 1 degree Celsius. Food Calories are kilocalories, equal to 1,000 calories. The energy of calories in food is burned off by many activities.

18 Figure 5.3 Food Food Calories Activity Food Calories consumed per hour by a 150-pound person* Cheeseburger 295 Running (7min/mi) 979 Spaghetti with sauce (1 cup) 241 Dancing (fast) 510 Baked potato (plain, with skin) 220 Bicycling (10 mph) 490 Fried chicken (drumstick) 193 Swimming (2 mph) 408 Bean burrito Pizza with pepperoni (1 slice) Peanuts (1 ounce) Apple Garden salad (2 cups) Popcorn (plain, 1 cup) Broccoli (1 cup) Walking (3 mph) Dancing (slow) Playing the piano Driving a car Sitting (writing) *Not including energy necessary for basic functions, such as breathing and heartbeat (a) Food Calories (kilocalories) in various foods (b) Food Calories (kilocalories) we burn in various activities

19 Figure 5.3a Food Food Calories Cheeseburger Spaghetti with sauce (1 cup) Baked potato (plain, with skin) Fried chicken (drumstick) Bean burrito Pizza with pepperoni (1 slice) Peanuts (1 ounce) Apple Garden salad (2 cups) Popcorn (plain, 1 cup) Broccoli (1 cup) (a) Food Calories (kilocalories) in various foods

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

21 ATP AND CELLULAR WORK Chemical energy is ATP released by the breakdown of organic molecules during cellular respiration and used to generate molecules of ATP. acts like an energy shuttle, stores energy obtained from food, and releases it later as needed.

22 The Structure of ATP ATP (adenosine triphosphate) consists of an organic molecule called adenosine plus a tail of three phosphate groups and is broken down to ADP and a phosphate group, releasing energy.

23 Blast Animation: Structure of ATP

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

25 Phosphate Transfer ATP energizes other molecules by transferring phosphate groups. This energy helps cells perform mechanical work, transport work, and chemical work.

26 Figure 5.5 Motor protein ATP ADP P ADP P Protein moved (a) Motor protein performing mechanical work (moving a muscle fiber) Transport protein Solute P P ATP ADP P Solute transported (b) Transport protein performing transport work (importing a solute) P ATP X P X Y ADP P Y Reactants Product made (c) Chemical reactants performing chemical work (promoting a chemical reaction)

27 Figure 5.5a Motor protein ATP ADP P ADP P Protein moved (a) Motor protein performing mechanical work (moving a muscle fiber)

28 Figure 5.5b Transport protein Solute P P ATP ADP P Solute transported (b) Transport protein performing transport work (importing a solute)

29 Figure 5.5c P ATP X P X Y ADP P Y Reactants Product made (c) Chemical reactants performing chemical work (promoting a chemical reaction)

30 The ATP Cycle Cellular work spends ATP continuously. ATP is recycled from ADP and a phosphate group through cellular respiration. A working muscle cell spends and recycles up to 10 million ATP molecules per second.

31 Blast Animation: ATP/ADP Cycle Select Play

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

33 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. All living cells contain thousands of different enzymes, each promoting a different chemical reaction.

34 Activation Energy Activation energy activates the reactants and triggers a chemical reaction. Enzymes reduce the amount of activation energy required to break bonds of reactant molecules.

35 Blast Animation: How Enzymes Work: Activation Energy Select Play

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

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

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

39 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 mimic this process through artificial selection? Hypothesis: An artificial process could be used to modify the gene that codes for lactase into a new gene coding for an enzyme with a new function.

40 The Process of Science: Can Enzymes Be Engineered? Experiment: Using the process of directed evolution, 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.

41 Figure 5.8 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 Ribbon model showing the polypeptide chains of the enzyme lactase After seven rounds, some genes code for enzymes that can efficiently perform new activity.

42 Figure 5.8a Gene for lactase Gene duplicated and mutated at random Mutated genes (mutations shown in orange)

43 Figure 5.8b 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.

44 Figure 5.8c Ribbon model showing the polypeptide chains of the enzyme lactase

45 Induced Fit An enzyme is very selective in the reaction it catalyzes. 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 because the entry of the substrate induces the enzyme to change shape slightly.

46 Induced Fit Enzymes can function over and over again, a key characteristic of enzymes. Many enzymes are named for their substrates, but with an ase ending.

47 Animation: How Enzymes Work Right click slide / select Play

48 Figure Active site 1 Ready for substrate Enzyme (sucrase)

49 Figure Substrate (sucrose) Active site 1 Ready for substrate 2 Substrate binding Enzyme (sucrase)

50 Figure Substrate (sucrose) Active site 1 Ready for substrate 2 Substrate binding Enzyme (sucrase) H 2 O 3 Catalysis

51 Figure Substrate (sucrose) Active site 1 Ready for substrate 2 Substrate binding Enzyme (sucrase) Fructose Glucose H 2 O 4 Product released 3 Catalysis

52 Enzyme Inhibitors Enzyme inhibitors can prevent metabolic reactions by binding to the active site or near the active site, resulting in changes to the enzyme s shape so that the active site no longer accepts the substrate.

53 Blast Animation: Enzyme Regulation: Competitive Inhibition Select Play

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

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

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

57 Figure 5.10c Active site Substrate Inhibitor Enzyme (c) Inhibition of an enzyme by a molecule that causes the active site to change shape

58 Enzyme Inhibitors 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 beneficial drugs work by inhibiting enzymes. Penicillin blocks the active site of an enzyme that bacteria use in making cell walls. Ibuprofen inhibits an enzyme involved in sending pain signals. Many cancer drugs inhibit enzymes that promote cell division.

59 MEMBRANE FUNCTION Cells must control the flow of materials to and from the environment. Membrane proteins perform many functions. Transport proteins are located in membranes and help move substances across a cell membrane.

60 Animation: Membrane Selectivity Right click slide / select Play

61 BioFlix Animation: Membrane Transport

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

63 Passive Transport: Diffusion across Membranes Molecules contain heat energy that causes them to vibrate and wander randomly. Diffusion is the movement of molecules so that they spread out evenly into the available space.

64 Passive Transport: Diffusion across Membranes Passive transport is the diffusion of a substance across a membrane without the input of energy. Cell membranes are selectively permeable, allowing only certain substances to pass. Substances diffuse down their concentration gradient, a region in which the substance s density changes.

65 Blast Animation: Diffusion Right click slide / select Play

66 Animation: Diffusion Right click slide / select Play

67 Blast Animation: Passive Diffusion Across a Membrane

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

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

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

71 Passive Transport: Diffusion across Membranes Some substances do not cross membranes spontaneously or cross slowly. These substances can be transported via facilitated diffusion. Specific transport proteins act as selective corridors. No energy input is needed.

72 Osmosis and Water Balance The diffusion of water across a selectively permeable membrane is osmosis.

73 Animation: Osmosis Right click slide / select Play

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

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

76 Osmosis and Water Balance Compared to another solution, a hypertonic solution has a higher concentration of solute, a hypotonic solution has a lower concentration of solute, and an isotonic solution has an equal concentration of solute.

77 Water Balance in Animal Cells Osmoregulation is the control of water balance within a cell or organism.

78 Water Balance in Plant Cells Plants have rigid cell walls. Plant cells are healthiest in a hypotonic environment, which keeps their walled cells turgid.

79 Video: Plasmolysis

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

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

82 Figure 5.14b H 2 O Lysing H 2 O Turgid (normal) (b) Hypotonic solution

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

84 Water Balance in Plant Cells As a plant cell loses water, it shrivels and its plasma membrane may pull away from the cell wall in the process of plasmolysis, which usually kills the cell.

85 Video: Turgid Elodea

86 Figure 5.15

87 Active Transport: The Pumping of Molecules across Membranes Active transport requires that a cell expend energy to move molecules across a membrane.

88 Blast Animation: Active Transport: Sodium-Potassium Pump

89 Animation: Active Transport Right click slide / select Play

90 Figure Lower solute concentration Solute ATP Higher solute concentration Active transport

91 Figure Lower solute concentration Solute ATP Higher solute concentration Active transport

92 Exocytosis and Endocytosis: Traffic of Large Molecules Exocytosis is the secretion of large molecules within transport vesicles.

93 Blast Animation: Endocytosis and Exocytosis

94 Animation: Exocytosis and Endocytosis Introduction Right click slide / select Play

95 Animation: Exocytosis Right click slide / select Play

96 Figure 5.17 Outside of cell Plasma membrane Cytoplasm Exocytosis

97 Exocytosis and Endocytosis: Traffic of Large Molecules Endocytosis takes material in via vesicles that bud inward from the plasma membrane.

98 Animation: Phagocytosis Right click slide / select Play

99 Animation: Pinocytosis Right click slide / select Play

100 Animation: Receptor-Mediated Endocytosis Right click slide / select Play

101 Figure 5.18 Endocytosis

102 Exocytosis and Endocytosis: Traffic of Large Molecules In the process of phagocytosis ( cellular eating ), a cell engulfs a particle and packages it within a food vacuole. Other times a cell gulps droplets of fluid into vesicles. Endocytosis can also be triggered by the binding of certain external molecules to specific receptor proteins built into the plasma membrane.

103 The Role of Membranes in Cell Signaling The plasma membrane helps convey signals between cells and between cells and their environment. Receptors on a cell surface trigger signal transduction pathways that relay the signal and convert it to chemical forms that can function within the cell.

104 Animation: Overview of Cell Signaling Right click slide / select Play

105 Animation: Signal Transduction Pathways Right click slide / select Play

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

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

108 Evolution Connection: The Origin of Membranes Phospholipids are key ingredients of membranes, were probably among the first organic compounds that formed from chemical reactions on early Earth, and self-assemble into simple membranes.

109 Figure 5.20 Water-filled bubble made of phospholipids

110 Figure 5.UN01 Energy for cellular work Adenosine P P P ATP Adenosine P P P cycle ATP Adenosine triphosphate Energy from organic fuel ADP Adenosine diphosphate Phosphate (can be transferred to another molecule)

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

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

113 Figure 5.UN04 Exocytosis Endocytosis