1. © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 5 The Working Cell

2. Figure 5.0_1 Chapter 5: Big Ideas Membrane Structure and Function Energy and the Cell How Enzymes Function Cellular respiration

3. Figure 5.0_2

4. Introduction  Bioluminescence is an example of the multitude of energy conversions that a cell can perform.  Many of a cell’s reactions –take place in organelles and –use enzymes embedded in the membranes of these organelles.  This chapter addresses how working cells use membranes, energy, and enzymes. © 2012 Pearson Education, Inc.

5. Figure 5.1 Fibers of extracellular matrix (ECM) Enzymatic activity Phospholipid Cholesterol CYTOPLASM Cell-cell recognition Glycoprotein Intercellular junctions Microfilaments of cytoskeleton ATP Transport Signal transduction Receptor Signaling molecule Attachment to the cytoskeleton and extracellular matrix (ECM)

6. 5.1 Membranes are fluid mosaics of lipids and proteins with many functions  Membranes are composed of –a bilayer of phospholipids with –embedded and attached proteins, –in a structure biologists call a fluid mosaic. © 2012 Pearson Education, Inc.

7. 5.1 Membranes are fluid mosaics of lipids and proteins with many functions  Many phospholipids are made from unsaturated fatty acids that have kinks in their tails.  These kinks prevent phospholipids from packing tightly together, keeping them in liquid form.  In animal cell membranes, cholesterol helps –stabilize membranes at warmer temperatures and –keep the membrane fluid at lower temperatures. © 2012 Pearson Education, Inc.

8. 5.1 Membranes are fluid mosaics of lipids and proteins with many functions  Membrane proteins perform many functions. 1.Some proteins help maintain cell shape and coordinate changes inside and outside the cell through their attachment to the cytoskeleton and extracellular matrix. 2.Some proteins function as receptors for chemical messengers from other cells. 3.Some membrane proteins function as enzymes. © 2012 Pearson Education, Inc.

9. 5.1 Membranes are fluid mosaics of lipids and proteins with many functions 4.Some membrane glycoproteins are involved in cell-cell recognition. 5.Membrane proteins may participate in the intercellular junctions that attach adjacent cells to each other. 6.Membranes may exhibit selective permeability, allowing some substances to cross more easily than others. © 2012 Pearson Education, Inc.

10. 5.2 EVOLUTION CONNECTION: Membranes form spontaneously, a critical step in the origin of life  Phospholipids, the key ingredient of biological membranes, spontaneously self-assemble into simple membranes.  The formation of membrane-enclosed collections of molecules was a critical step in the evolution of the first cells. © 2012 Pearson Education, Inc.

11. Figure 5.2 Water-filled bubble made of phospholipids

12. Concept Check Membranes organize cell activities. The proteins imbedded in the membranes are essential to their function. These membrane proteins have properties that allow them to “float” in the membrane. Which of the following statements describes those properties? a)The surface region of the protein in the interior of the membrane is mostly hydrophobic. b)The surface region of the protein in the interior of the membrane is mostly hydrophillic. c)The surface region exposed to the outer environment is hydrophobic. d)The surface region exposed to the interior environment is hydrophobic. © 2012 Pearson Education, Inc.

13. Answer Membranes organize cell activities. The proteins imbedded in the membranes are essential to their function. These membrane proteins have properties that allow them to “float” in the membrane. Which of the following statements describes those properties? a)The surface region of the protein in the interior of the membrane is mostly hydrophobic. © 2012 Pearson Education, Inc.

14. Figure 5.2Q Water

15. 5.3 Passive transport is diffusion across a membrane with no energy investment  Diffusion is the tendency of particles to spread out evenly in an available space. –Particles move from an area of more concentrated particles to an area where they are less concentrated. –This means that particles diffuse down their concentration gradient. –Eventually, the particles reach equilibrium where the concentration of particles is the same throughout. © 2012 Pearson Education, Inc.

16. 5.3 Passive transport is diffusion across a membrane with no energy investment  Diffusion across a cell membrane does not require energy, so it is called passive transport.  The concentration gradient itself represents potential energy for diffusion. © 2012 Pearson Education, Inc. Animation: Diffusion

17. Figure 5.3A Molecules of dye Membrane Pores Net diffusion Equilibrium

18. Figure 5.3B Net diffusion Equilibrium

19. 5.4 Osmosis is the diffusion of water across a membrane  One of the most important substances that crosses membranes is water.  The diffusion of water across a selectively permeable membrane is called osmosis. © 2012 Pearson Education, Inc. Animation: Osmosis

20. 5.4 Osmosis is the diffusion of water across a membrane  If a membrane permeable to water but not a solute separates two solutions with different concentrations of solute, –water will cross the membrane, –moving down its own concentration gradient, –until the solute concentration on both sides is equal. © 2012 Pearson Education, Inc.

21. Figure 5.4 Osmosis Solute molecule with cluster of water molecules Water molecule Selectively permeable membrane Solute molecule H2OH2O Lower concentration of solute Higher concentration of solute Equal concentrations of solute

22. 5.5 Water balance between cells and their surroundings is crucial to organisms  Tonicity is a term that describes the ability of a solution to cause a cell to gain or lose water.  Tonicity mostly depends on the concentration of a solute on both sides of the membrane. © 2012 Pearson Education, Inc.

23. 5.5 Water balance between cells and their surroundings is crucial to organisms  How will animal cells be affected when placed into solutions of various tonicities? When an animal cell is placed into –an isotonic solution, the concentration of solute is the same on both sides of a membrane, and the cell volume will not change, –a hypotonic solution, the solute concentration is lower outside the cell, water molecules move into the cell, and the cell will expand and may burst, or –a hypertonic solution, the solute concentration is higher outside the cell, water molecules move out of the cell, and the cell will shrink. © 2012 Pearson Education, Inc.

24. 5.5 Water balance between cells and their surroundings is crucial to organisms  For an animal cell to survive in a hypotonic or hypertonic environment, it must engage in osmoregulation, the control of water balance. © 2012 Pearson Education, Inc.

25. Concept Check This diagram represents osmosis of water across a semipermeable membrane. The U-tube on the right shows the results of the osmosis. What could you do to level the solutions in the two sides of the U-tube on the right? a)Add more water to the left- hand side. b)Add more water to the right- hand side. c)Add more solute to the left- hand side. d)Add more solute to the right- hand side. © 2012 Pearson Education, Inc.

26. Answer This diagram represents osmosis of water across a semipermeable membrane. The U-tube on the right shows the results of the osmosis. What could you do to level the solutions in the two sides of the U-tube on the right? c)Add more solute to the left- hand side. © 2012 Pearson Education, Inc.

27. 5.5 Water balance between cells and their surroundings is crucial to organisms  The cell walls of plant cells, prokaryotes, and fungi make water balance issues somewhat different. –The cell wall of a plant cell exerts pressure that prevents the cell from taking in too much water and bursting when placed in a hypotonic environment. –But in a hypertonic environment, plant and animal cells both shrivel. © 2012 Pearson Education, Inc. Video: Paramecium Vacuole Video: Plasmolysis

28. Figure 5.5 Animal cell Plant cell Turgid (normal) Flaccid Shriveled (plasmolyzed) Plasma membrane Lysed NormalShriveled Hypotonic solution Isotonic solution Hypertonic solution H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O

29. 5.6 Transport proteins can facilitate diffusion across membranes  Hydrophobic substances easily diffuse across a cell membrane.  However, polar or charged substances do not easily cross cell membranes and, instead, move across membranes with the help of specific transport proteins in a process called facilitated diffusion, which –does not require energy and –relies on the concentration gradient. © 2012 Pearson Education, Inc.

30. 5.6 Transport proteins can facilitate diffusion across membranes  Some proteins function by becoming a hydrophilic tunnel for passage of ions or other molecules.  Other proteins bind their passenger, change shape, and release their passenger on the other side.  In both of these situations, the protein is specific for the substrate, which can be sugars, amino acids, ions, and even water. © 2012 Pearson Education, Inc.

31. 5.6 Transport proteins can facilitate diffusion across membranes  Because water is polar, its diffusion through a membrane’s hydrophobic interior is relatively slow.  The very rapid diffusion of water into and out of certain cells is made possible by a protein channel called an aquaporin. © 2012 Pearson Education, Inc.

32. Figure 5.6 Solute molecule Transport protein

33. 5.7 SCIENTIFIC DISCOVERY: Research on another membrane protein led to the discovery of aquaporins  Dr. Peter Agre received the 2003 Nobel Prize in chemistry for his discovery of aquaporins.  His research on the Rh protein used in blood typing led to this discovery. © 2012 Pearson Education, Inc.

34. Figure 5.7

35. 5.8 Cells expend energy in the active transport of a solute  In active transport, a cell –must expend energy to –move a solute against its concentration gradient.  The following figures show the four main stages of active transport. © 2012 Pearson Education, Inc. Animation: Active Transport

36. Figure 5.8_s1 Transport protein Solute Solute binding 1

37. Figure 5.8_s2 Transport protein Solute ADP ATP P Solute binding Phosphate attaching 2 1

38. Figure 5.8_s3 Transport protein Solute ADP ATP P P Protein changes shape. Solute binding Phosphate attaching Transport 2 1 3

39. Figure 5.8_s4 Transport protein Solute ADP ATP P P P Protein changes shape. Phosphate detaches. Solute binding Phosphate attaching TransportProtein reversion 4 32 1

40. 5.9 Exocytosis and endocytosis transport large molecules across membranes  A cell uses two mechanisms to move large molecules across membranes. –Exocytosis is used to export bulky molecules, such as proteins or polysaccharides. –Endocytosis is used to import substances useful to the livelihood of the cell.  In both cases, material to be transported is packaged within a vesicle that fuses with the membrane. © 2012 Pearson Education, Inc.

41. 5.9 Exocytosis and endocytosis transport large molecules across membranes  There are three kinds of endocytosis. 1.Phagocytosis is the engulfment of a particle by wrapping cell membrane around it, forming a vacuole. 2.Pinocytosis is the same thing except that fluids are taken into small vesicles. 3.Receptor-mediated endocytosis uses receptors in a receptor-coated pit to interact with a specific protein, initiating the formation of a vesicle. © 2012 Pearson Education, Inc.

42. Figure 5.9 Phagocytosis Pinocytosis Receptor-mediated endocytosis EXTRACELLULAR FLUID CYTOPLASM Pseudopodium “Food” or other particle Food vacuole Food being ingested Plasma membrane Vesicle Receptor Specific molecule Coated pit Coated vesicle Coat protein Coated pit Material bound to receptor proteins

43. Figure 5.9_1 Phagocytosis EXTRACELLULAR FLUID CYTOPLASM Pseudopodium “Food” or other particle Food vacuole Food being ingested

44. Figure 5.9_2 Pinocytosis Plasma membrane Vesicle

45. Figure 5.9_3 Receptor-mediated endocytosis Plasma membrane Receptor Specific molecule Coated pit Coated vesicle Coat protein Coated pit Material bound to receptor proteins

46. Figure 5.9_4 Food being ingested

47. Figure 5.9_5 Plasma membrane

48. Figure 5.9_6 Plasma membrane Coated pit Material bound to receptor proteins

49. ENERGY AND THE CELL © 2012 Pearson Education, Inc.

50. 5.10 Cells transform energy as they perform work  Cells are small units, a chemical factory, housing thousands of chemical reactions.  Cells use these chemical reactions for –cell maintenance, –manufacture of cellular parts, and –cell replication. © 2012 Pearson Education, Inc.

51. 5.10 Cells transform energy as they perform work  Energy is the capacity to cause change or to perform work.  There are two kinds of energy. 1.Kinetic energy is the energy of motion. 2.Potential energy is energy that matter possesses as a result of its location or structure. © 2012 Pearson Education, Inc.

52. Figure 5.10 Fuel Energy conversion Waste products Gasoline Oxygen Glucose     Heat energy Combustion Kinetic energy of movement Energy conversion in a car Energy conversion in a cell Energy for cellular work Cellular respiration ATP Heat energy Carbon dioxide Water

53. 5.10 Cells transform energy as they perform work  Heat, or thermal energy, is a type of kinetic energy associated with the random movement of atoms or molecules.  Light is also a type of kinetic energy, and can be harnessed to power photosynthesis. © 2012 Pearson Education, Inc.

54. 5.10 Cells transform energy as they perform work  Chemical energy is the potential energy available for release in a chemical reaction. It is the most important type of energy for living organisms to power the work of the cell. © 2012 Pearson Education, Inc. Animation: Energy Concepts

55. 5.10 Cells transform energy as they perform work  Thermodynamics is the study of energy transformations that occur in a collection of matter.  Scientists use the word –system for the matter under study and –surroundings for the rest of the universe. © 2012 Pearson Education, Inc.

56. 5.10 Cells transform energy as they perform work  Two laws govern energy transformations in organisms. According to the –first law of thermodynamics, energy in the universe is constant, and –second law of thermodynamics, energy conversions increase the disorder of the universe.  Entropy is the measure of disorder, or randomness. © 2012 Pearson Education, Inc.

57. 5.10 Cells transform energy as they perform work  Cells use oxygen in reactions that release energy from fuel molecules.  In cellular respiration, the chemical energy stored in organic molecules is converted to a form that the cell can use to perform work. © 2012 Pearson Education, Inc.

58. 5.11 Chemical reactions either release or store energy  Chemical reactions either –release energy (exergonic reactions) or –require an input of energy and store energy (endergonic reactions). © 2012 Pearson Education, Inc.

59. 5.11 Chemical reactions either release or store energy  Exergonic reactions release energy. –These reactions release the energy in covalent bonds of the reactants. –Burning wood releases the energy in glucose as heat and light. –Cellular respiration –involves many steps, –releases energy slowly, and –uses some of the released energy to produce ATP. © 2012 Pearson Education, Inc.

60. Figure 5.11A Reactants Energy Products Amount of energy released Potential energy of molecules

61. 5.11 Chemical reactions either release or store energy  An endergonic reaction –requires an input of energy and –yields products rich in potential energy.  Endergonic reactions –begin with reactant molecules that contain relatively little potential energy but –end with products that contain more chemical energy. © 2012 Pearson Education, Inc.

62. Figure 5.11B Reactants Energy Products Amount of energy required Potential energy of molecules

63. 5.11 Chemical reactions either release or store energy  Photosynthesis is a type of endergonic process. –Energy-poor reactants, carbon dioxide, and water are used. –Energy is absorbed from sunlight. –Energy-rich sugar molecules are produced. © 2012 Pearson Education, Inc.

64. 5.11 Chemical reactions either release or store energy  A living organism carries out thousands of endergonic and exergonic chemical reactions.  The total of an organism’s chemical reactions is called metabolism.  A metabolic pathway is a series of chemical reactions that either –builds a complex molecule or –breaks down a complex molecule into simpler compounds. © 2012 Pearson Education, Inc.

65. 5.11 Chemical reactions either release or store energy  Energy coupling uses the –energy released from exergonic reactions to drive –essential endergonic reactions, –usually using the energy stored in ATP molecules. © 2012 Pearson Education, Inc.

66.  ATP, adenosine triphosphate, powers nearly all forms of cellular work.  ATP consists of –the nitrogenous base adenine, –the five-carbon sugar ribose, and –three phosphate groups. 5.12 ATP drives cellular work by coupling exergonic and endergonic reactions © 2012 Pearson Education, Inc.

67. 5.12 ATP drives cellular work by coupling exergonic and endergonic reactions  Hydrolysis of ATP releases energy by transferring its third phosphate from ATP to some other molecule in a process called phosphorylation.  Most cellular work depends on ATP energizing molecules by phosphorylating them. © 2012 Pearson Education, Inc.

68. Figure 5.12A_s1 Adenine P P P Phosphate group ATP:Adenosine Triphosphate Ribose

69. Figure 5.12A_s2 ADP: Adenosine Diphosphate P P P Energy H2OH2O Hydrolysis Ribose Adenine P P P Phosphate group ATP:Adenosine Triphosphate

70. 5.12 ATP drives cellular work by coupling exergonic and endergonic reactions  There are three main types of cellular work: 1.chemical, 2.mechanical, and 3.transport.  ATP drives all three of these types of work. © 2012 Pearson Education, Inc.

71. Figure 5.12B ATP ADP P P P P P P P P P Chemical work Mechanical workTransport work Reactants Motor protein Solute Membrane protein Product Molecule formed Protein filament moved Solute transported

72. 5.12 ATP drives cellular work by coupling exergonic and endergonic reactions  ATP is a renewable source of energy for the cell.  In the ATP cycle, energy released in an exergonic reaction, such as the breakdown of glucose,is used in an endergonic reaction to generate ATP. © 2012 Pearson Education, Inc.

73. Figure 5.12C Energy from exergonic reactions Energy for endergonic reactions ATP ADP P

74. HOW ENZYMES FUNCTION © 2012 Pearson Education, Inc.

75. 5.13 Enzymes speed up the cell’s chemical reactions by lowering energy barriers  Although biological molecules possess much potential energy, it is not released spontaneously. –An energy barrier must be overcome before a chemical reaction can begin. –This energy is called the activation energy (E A ). © 2012 Pearson Education, Inc.

76. 5.13 Enzymes speed up the cell’s chemical reactions by lowering energy barriers  We can think of E A –as the amount of energy needed for a reactant molecule to move “uphill” to a higher energy but an unstable state –so that the “downhill” part of the reaction can begin.  One way to speed up a reaction is to add heat, –which agitates atoms so that bonds break more easily and reactions can proceed but –could kill a cell. © 2012 Pearson Education, Inc.

77. Figure 5.13A Activation energy barrier Reactant Products Without enzyme With enzyme Reactant Products Enzyme Activation energy barrier reduced by enzyme Energy

78. Figure 5.13A_1 Activation energy barrier Reactant Products Without enzyme Energy

79. Figure 5.13A_2 Activation energy barrier reduced by enzyme Reactant Products With enzyme Energy Enzyme

80. Figure 5.13Q Reactants Products Energy Progress of the reaction a b c

81. 5.13 Enzymes speed up the cell’s chemical reactions by lowering energy barriers  Enzymes –function as biological catalysts by lowering the E A needed for a reaction to begin, –increase the rate of a reaction without being consumed by the reaction, and –are usually proteins, although some RNA molecules can function as enzymes. © 2012 Pearson Education, Inc. Animation: How Enzymes Work

82. 5.14 A specific enzyme catalyzes each cellular reaction  An enzyme –is very selective in the reaction it catalyzes and –has a shape that determines the enzyme’s specificity.  The specific reactant that an enzyme acts on is called the enzyme’s substrate.  A substrate fits into a region of the enzyme called the active site.  Enzymes are specific because their active site fits only specific substrate molecules. © 2012 Pearson Education, Inc.

83. 5.14 A specific enzyme catalyzes each cellular reaction  The following figure illustrates the catalytic cycle of an enzyme. © 2012 Pearson Education, Inc.

84. Figure 5.14_s1 1 Enzyme (sucrase) Active site Enzyme available with empty active site

85. Figure 5.14_s2 2 1 Enzyme (sucrase) Active site Enzyme available with empty active site Substrate (sucrose) Substrate binds to enzyme with induced fit

86. Figure 5.14_s3 32 1 Enzyme (sucrase) Active site Enzyme available with empty active site Substrate (sucrose) Substrate binds to enzyme with induced fit Substrate is converted to products H2OH2O

87. Figure 5.14_s4 4 32 1 Products are released Fructose Glucose Enzyme (sucrase) Active site Enzyme available with empty active site Substrate (sucrose) Substrate binds to enzyme with induced fit Substrate is converted to products H2OH2O

88. 5.14 A specific enzyme catalyzes each cellular reaction  For every enzyme, there are optimal conditions under which it is most effective.  Temperature affects molecular motion. –An enzyme’s optimal temperature produces the highest rate of contact between the reactants and the enzyme’s active site. –Most human enzymes work best at 35–40ºC.  The optimal pH for most enzymes is near neutrality. © 2012 Pearson Education, Inc.

89. 5.14 A specific enzyme catalyzes each cellular reaction  Many enzymes require nonprotein helpers called cofactors, which –bind to the active site and –function in catalysis.  Some cofactors are inorganic, such as zinc, iron, or copper.  If a cofactor is an organic molecule, such as most vitamins, it is called a coenzyme. © 2012 Pearson Education, Inc.

90. 5.15 Enzyme inhibitors can regulate enzyme activity in a cell  A chemical that interferes with an enzyme’s activity is called an inhibitor.  Competitive inhibitors –block substrates from entering the active site and –reduce an enzyme’s productivity. © 2012 Pearson Education, Inc.

91. 5.15 Enzyme inhibitors can regulate enzyme activity in a cell  Noncompetitive inhibitors –bind to the enzyme somewhere other than the active site, –change the shape of the active site, and –prevent the substrate from binding. © 2012 Pearson Education, Inc.

92. Figure 5.15A Substrate Enzyme Allosteric site Active site Normal binding of substrate Competitive inhibitor Noncompetitive inhibitor Enzyme inhibition

93. 5.15 Enzyme inhibitors can regulate enzyme activity in a cell  Enzyme inhibitors are important in regulating cell metabolism.  In some reactions, the product may act as an inhibitor of one of the enzymes in the pathway that produced it. This is called feedback inhibition. © 2012 Pearson Education, Inc.

94. Figure 5.15B Feedback inhibition Starting molecule Product Enzyme 1 Enzyme 2 Enzyme 3 Reaction 1 Reaction 2 Reaction 3 A B C D

95. 5.16 CONNECTION: Many drugs, pesticides, and poisons are enzyme inhibitors  Many beneficial drugs act as enzyme inhibitors, including –Ibuprofen, inhibiting the production of prostaglandins, –some blood pressure medicines, –some antidepressants, –many antibiotics, and –protease inhibitors used to fight HIV.  Enzyme inhibitors have also been developed as pesticides and deadly poisons for chemical warfare. © 2012 Pearson Education, Inc.

96. Concept Check Enzymes catalyze the many reactions in a cell. There are hundreds of different enzymes in a cell—each with a unique three-dimensional shape. Why do cells have so many different enzymes? a)Each enzyme molecule can only be used once. b)The shape of an enzyme’s active site generally fits a specific substrate. c)The substrate molecules react with enzymes to create new enzymes. d)Enzymes are randomly produced. With thousands of different shapes— one is likely to work. © 2012 Pearson Education, Inc.

97. Answer Enzymes catalyze the many reactions in a cell. There are hundreds of different enzymes in a cell—each with a unique three-dimensional shape. Why do cells have so many different enzymes? b)The shape of an enzyme’s active site generally fits a specific substrate. © 2012 Pearson Education, Inc.

98. Interpreting Data This graph illustrates how an enzyme catalyzes reactions in biological systems. From an energy standpoint, is this reaction an endergonic or exergonic reaction? a)Endergonic. b)Exergonic. c)There is not enough information in this graph to decide the type of reaction. © 2012 Pearson Education, Inc.

99. Answer This graph illustrates how an enzyme catalyzes reactions in biological systems. From an energy standpoint, is this reaction an endergonic or exergonic reaction? b)Exergonic. © 2012 Pearson Education, Inc.

100. Interpreting Data Which of the following represents the energy of activation that is modified by an enzyme? a)a b)b c)c © 2012 Pearson Education, Inc.

101. Interpreting Data In order to start an exergonic reaction, a certain amount of energy must be absorbed by the reactants. This is called the energy of activation. Which of the following is the normal energy of activation? a)a © 2012 Pearson Education, Inc.

102. 1.Describe the fluid mosaic structure of cell membranes. 2.Describe the diverse functions of membrane proteins. 3.Relate the structure of phospholipid molecules to the structure and properties of cell membranes. 4.Define diffusion and describe the process of passive transport. You should now be able to © 2012 Pearson Education, Inc.

103. 5.Explain how osmosis can be defined as the diffusion of water across a membrane. 6.Distinguish between hypertonic, hypotonic, and isotonic solutions. 7.Explain how transport proteins facilitate diffusion. 8.Distinguish between exocytosis, endocytosis, phagocytosis, pinocytosis, and receptor-mediated endocytosis. You should now be able to © 2012 Pearson Education, Inc.

104. 9.Define and compare kinetic energy, potential energy, chemical energy, and heat. 10.Define the two laws of thermodynamics and explain how they relate to biological systems. 11.Define and compare endergonic and exergonic reactions. 12.Explain how cells use cellular respiration and energy coupling to survive. You should now be able to © 2012 Pearson Education, Inc.

105. You should now be able to 13.Explain how ATP functions as an energy shuttle. 14.Explain how enzymes speed up chemical reactions. 15.Explain how competitive and noncompetitive inhibitors alter an enzyme’s activity. 16.Explain how certain drugs, pesticides, and poisons can affect enzymes. © 2012 Pearson Education, Inc.

106. Figure 5.UN02 ATP cycle ATP ADP P Energy from exergonic reactions Energy for endergonic reactions

107. Figure 5.UN03 Molecules cross cell membranes passive transport polar molecules and ions diffusion moving down moving against requires by may be uses of ATP (a) (b) (c) (d) (e)

108. Figure 5.UN04 a. b. c. d. e. f.

109. Table 5.UN05

110. Figure 5.UN06 pH Rate of reaction 10 9 87 6 54 3 21 0