1. An Introduction to Metabolism
Chapter 8
An Introduction to Metabolism

2. Overview: The Energy of Life
The living cell is a miniature chemical factory where thousands of reactions occur
The cell extracts energy and applies energy to perform work
Some organisms even convert stored energy in certain organic molecules to light, as in bioluminescence
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3. Figure 8.1
Figure 8.1 What causes these two squid to glow? 3

4. Concept 8.1: An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics
Metabolism is the totality of an organism’s chemical reactions
Metabolism is an emergent property of life that arises from interactions between molecules within the cell
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5. Organization of the Chemistry of Life into Metabolic Pathways
A metabolic pathway begins with a specific molecule and ends with a product
Each step of the pathway is catalyzed by a specific enzyme.
ex). Traffic light regulates traffic flow mechanisms that regulate enzymes, balance metabolic supply and demand.
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6. Figure 8.UN01
Enzyme 1
Enzyme 2
Enzyme 3 A B C D
Reaction 1
Reaction 2
Reaction 3
Starting molecule
Product
Figure 8.UN01 In-text figure, p. 142
Enzymes speed up each reaction in a series of reactions to in order to obtain the product at a much quicker rate. 6

7. Metabolism as a whole manages the material and energy resources of the cell.
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8. Catabolic pathways release energy by breaking down complex molecules into simpler compounds
A major pathway of catabolism is cellular respiration, the breakdown of glucose in the presence of oxygen to carbon dioxide and water, is an example of a pathway of catabolism.
Metabolism as a whole manages the material and energy resources of the cell.
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9. The synthesis of protein from amino acids is an example of anabolism
Anabolic pathways consume energy to build complex molecules from simpler ones
The synthesis of protein from amino acids is an example of anabolism
Bioenergetics is the study of how organisms manage their energy resources
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10. Forms of Energy
Energy is the capacity to cause change or the ability to rearrange matter.
Energy exists in various forms, some of which can perform work.
Energy expenditure (turning pages of this book?
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11. Energy can be converted from one form to another
Kinetic energy is energy associated with motion of objects. Ex)playing pool
Heat (thermal energy) is kinetic energy associated with random movement of atoms or molecules harnessed to do work. Also in light which powers (photosynthesis)
Potential energy is energy that matter possesses because of its location or structure
Chemical energy is potential energy availablefor release in a chemical reaction
Energy can be converted from one form to another
Animation: Energy Concepts
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12. A diver has more potential energy on the platform than in the water.
Figure 8.2
A diver has more potential energy on the platform than in the water.
Diving converts potential energy to kinetic energy.
Figure 8.2 Transformations between potential and kinetic energy.
Climbing up converts the kinetic energy of muscle movement to potential energy.
A diver has less potential energy in the water than on the platform. 12

13. The Laws of Energy Transformation
Thermodynamics is the study of energy transformations
A isolated system, such as that approximated by liquid in a thermos, is isolated and is unable to exchange either energy or matter with its surroundings
In an open system, energy and matter can be transferred between the system and its surroundings
Organisms are open systems – absorb energy in the form of organic molecules, but release energy in the form of heat and waste, carbon dioxide and water.
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14. The First Law of Thermodynamics
According to the first law of thermodynamics, the energy of the universe is constant
Energy can be transferred and transformed, but it cannot be created or destroyed
The first law is also called the principle of conservation of energy
Electric company does not make energy, converts it into a form we can use.
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15. The Second Law of Thermodynamics
During every energy transfer or transformation, some energy is unusable, and is often lost as heat or waste (carbon dioxide)
According to the second law of thermodynamics
Every energy transfer or transformation increases the entropy (disorder) randomness) of the universe
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16. Figure 8.3
A brown bear converts chemical energy from organic molecules in its food into kinetic and other forms of energy to carry out biological processes.
Heat
Chemical energy
Figure 8.3 The two laws of thermodynamics.
(a) First law of thermodynamics
(b) Second law of thermodynamics 16

17. Living cells unavoidably convert organized forms of energy to heat
Spontaneous processes occur without energy input; they can happen quickly or slowly
For a process to occur without energy input, it must increase the entropy of the universe
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18. Biological Order and Disorder
Cells create ordered structures from less ordered materials
Organisms also replace ordered forms of matter and energy with less ordered forms
Energy flows into an ecosystem in the form of light and exits in the form of heat
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19. Concept 8.2: The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously
Biologists want to know which reactions occur spontaneously and which require input of energy
To do so, they need to determine energy changes that occur in chemical reactions
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20. Free-Energy Change, G
A living system’s free energy is energy that can do work when temperature and pressure are uniform, as in a living cell
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21. Only processes with a negative ∆G are spontaneous
The change in free energy (∆G) during a process is related to the change in enthalpy, or change in total energy (∆H), change in entropy (∆S), and temperature in Kelvin (T)
∆G = ∆H – T∆S
Only processes with a negative ∆G are spontaneous
Spontaneous processes can be harnessed to perform work
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22. Free Energy, Stability, and Equilibrium
Free energy is a measure of a system’s instability, its tendency to change to a more stable state
During a spontaneous change, free energy decreases and the stability of a system increases
Equilibrium is a state of maximum stability
A process is spontaneous and can perform work only when it is moving toward equilibrium
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23. Figure 8.5
• More free energy (higher G) • Less stable • Greater work capacity
In a spontaneous change • The free energy of the system decreases (G  0) • The system becomes more stable • The released free energy can be harnessed to do work
• Less free energy (lower G) • More stable • Less work capacity
Figure 8.5 The relationship of free energy to stability, work capacity, and spontaneous change.
(a) Gravitational motion
(b) Diffusion
(c) Chemical reaction 23

24. • More free energy (higher G) • Less stable • Greater work capacity
Figure 8.5a
• More free energy (higher G) • Less stable • Greater work capacity
In a spontaneous change • The free energy of the system decreases (G  0) • The system becomes more stable • The released free energy can be harnessed to do work
Figure 8.5 The relationship of free energy to stability, work capacity, and spontaneous change.
• Less free energy (lower G) • More stable • Less work capacity 24

25. (a) Gravitational motion (b) Diffusion (c) Chemical reaction
Figure 8.5b
Figure 8.5 The relationship of free energy to stability, work capacity, and spontaneous change.
(a) Gravitational motion
(b) Diffusion
(c) Chemical reaction 25

26. Free Energy and Metabolism
The concept of free energy can be applied to the chemistry of life’s processes
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27. Exergonic and Endergonic Reactions in Metabolism
An exergonic reaction proceeds with a net release of free energy and is spontaneous
An endergonic reaction absorbs free energy from its surroundings and is nonspontaneous
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28. Amount of energy released (G  0) Amount of energy required (G  0)
Figure 8.6
(a) Exergonic reaction: energy released, spontaneous
Reactants
Amount of energy released (G  0)
Free energy
Energy
Products
Progress of the reaction
(b) Endergonic reaction: energy required, nonspontaneous
Products
Figure 8.6 Free energy changes (G) in exergonic and endergonic reactions.
Amount of energy required (G  0)
Free energy
Energy
Reactants
Progress of the reaction 28

29. Amount of energy released (G  0)
Figure 8.6a
(a) Exergonic reaction: energy released, spontaneous
Reactants
Amount of energy released (G  0)
Energy
Free energy
Products
Figure 8.6 Free energy changes (G) in exergonic and endergonic reactions.
Progress of the reaction 29

30. Amount of energy required (G  0)
Figure 8.6b
(b) Endergonic reaction: energy required, nonspontaneous
Products
Amount of energy required (G  0)
Energy
Free energy
Reactants
Figure 8.6 Free energy changes (G) in exergonic and endergonic reactions.
Progress of the reaction 30

31. Equilibrium and Metabolism
Reactions in a closed system eventually reach equilibrium and then do no work
Cells are not in equilibrium; they are open systems experiencing a constant flow of materials
A defining feature of life is that metabolism is never at equilibrium
A catabolic pathway in a cell releases free energy in a series of reactions
Closed and open hydroelectric systems can serve as analogies
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32. (a) An isolated hydroelectric system
Figure 8.7
G  0
G  0
(a) An isolated hydroelectric system
(b) An open hydro electric system
G  0
Figure 8.7 Equilibrium and work in isolated and open systems.
G  0
G  0
G  0
(c) A multistep open hydroelectric system 32

33. (a) An isolated hydroelectric system
Figure 8.7a
G  0
G  0
Figure 8.7 Equilibrium and work in isolated and open systems.
(a) An isolated hydroelectric system 33

34. (b) An open hydroelectric system
Figure 8.7b
(b) An open hydroelectric system
G  0
Figure 8.7 Equilibrium and work in isolated and open systems. 34

35. (c) A multistep open hydroelectric system
Figure 8.7c
G  0
G  0
G  0
Figure 8.7 Equilibrium and work in isolated and open systems.
(c) A multistep open hydroelectric system 35

36. Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions
A cell does three main kinds of work
Chemical
Transport
Mechanical
To do work, cells manage energy resources by energy coupling, the use of an exergonic process to drive an endergonic one
Most energy coupling in cells is mediated by ATP
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37. The Structure and Hydrolysis of ATP
ATP (adenosine triphosphate) is the cell’s energy shuttle
ATP is composed of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups
For the Cell Biology Video Space Filling Model of ATP (Adenosine Triphosphate), go to Animation and Video Files.
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38. Figure 8.8
Adenine
Phosphate groups
Ribose
(a) The structure of ATP
Adenosine triphosphate (ATP)
Figure 8.8 The structure and hydrolysis of adenosine triphosphate (ATP).
Energy
Inorganic phosphate
Adenosine diphosphate (ADP)
(b) The hydrolysis of ATP 38

39. (a) The structure of ATP
Figure 8.8a
Adenine
Phosphate groups
Ribose
Figure 8.8 The structure and hydrolysis of adenosine triphosphate (ATP).
(a) The structure of ATP 39

40. Adenosine triphosphate (ATP)
Figure 8.8b
Adenosine triphosphate (ATP)
Figure 8.8 The structure and hydrolysis of adenosine triphosphate (ATP).
Energy
Inorganic phosphate
Adenosine diphosphate (ADP)
(b) The hydrolysis of ATP 40

41. Energy is released from ATP when the terminal phosphate bond is broken
The bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis
Energy is released from ATP when the terminal phosphate bond is broken
This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves
For the Cell Biology Video Stick Model of ATP (Adenosine Triphosphate), go to Animation and Video Files.
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42. How the Hydrolysis of ATP Performs Work
The three types of cellular work (mechanical, transport, and chemical) are powered by the hydrolysis of ATP
In the cell, the energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction
Overall, the coupled reactions are exergonic
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43. Phosphorylated intermediate
Figure 8.9
Glutamic acid conversion to glutamine
(a)
NH3
NH2
GGlu = +3.4 kcal/mol
Glu
Glu
Glutamic acid
Ammonia
Glutamine
(b)
Conversion reaction coupled with ATP hydrolysis
NH3 1 P 2
ADP
NH2
ADP
ATP
P i
Glu
Glu
Glu
Glutamic acid
Phosphorylated intermediate
Glutamine
GGlu = +3.4 kcal/mol
(c)
Free-energy change for coupled reaction
Figure 8.9 How ATP drives chemical work: Energy coupling using ATP hydrolysis.
NH3
NH2
ATP
ADP
P i
Glu
Glu
GGlu = +3.4 kcal/mol
GATP = 7.3 kcal/mol
+ GATP = 7.3 kcal/mol
Net G = 3.9 kcal/mol 43

44. The recipient molecule is now called a phosphorylated intermediate
ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant
The recipient molecule is now called a phosphorylated intermediate
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45. Protein and vesicle moved
Figure 8.10
Transport protein
Solute
ATP
ADP
P i P
P i
Solute transported
(a) Transport work: ATP phosphorylates transport proteins.
Vesicle
Cytoskeletal track
Figure 8.10 How ATP drives transport and mechanical work.
ATP
ADP
P i
ATP
Motor protein
Protein and vesicle moved
(b) Mechanical work: ATP binds noncovalently to motor proteins and then is hydrolyzed. 45

46. The Regeneration of ATP
ATP is a renewable resource that is regenerated by addition of a phosphate group to adenosine diphosphate (ADP)
The energy to phosphorylate ADP comes from catabolic reactions in the cell
The ATP cycle is a revolving door through which energy passes during its transfer from catabolic to anabolic pathways
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47. Energy from catabolism (exergonic, energy-releasing processes)
Figure 8.11
ATP
H2O
Energy from catabolism (exergonic, energy-releasing processes)
Energy for cellular work (endergonic, energy-consuming processes)
Figure 8.11 The ATP cycle.
ADP
P i 47

48. Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers
A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction
An enzyme is a catalytic protein
Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction
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49. Sucrose (C12H22O11) Glucose (C6H12O6) Fructose (C6H12O6)
Figure 8.UN02
Sucrase
Sucrose (C12H22O11)
Glucose (C6H12O6)
Fructose (C6H12O6)
Figure 8.UN02 In-text figure, p. 152 49

50. The Activation Energy Barrier
Every chemical reaction between molecules involves bond breaking and bond forming
The initial energy needed to start a chemical reaction is called the free energy of activation, or activation energy (EA)
Activation energy is often supplied in the form of thermal energy that the reactant molecules absorb from their surroundings
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51. Progress of the reaction
Figure 8.12 A B C D
Transition state A B EA
Free energy C D
Reactants A B
Figure 8.12 Energy profile of an exergonic reaction.
G  O C D
Products
Progress of the reaction 51

52. How Enzymes Lower the EA Barrier
Enzymes catalyze reactions by lowering the EA barrier
Enzymes do not affect the change in free energy (∆G); instead, they hasten reactions that would occur eventually
Animation: How Enzymes Work
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53. Course of reaction without enzyme EA without enzyme
Figure 8.13
Course of reaction without enzyme
EA without enzyme
EA with enzyme is lower
Reactants
Free energy
Course of reaction with enzyme
G is unaffected by enzyme
Figure 8.13 The effect of an enzyme on activation energy.
Products
Progress of the reaction 53

54. Substrate Specificity of Enzymes
The reactant that an enzyme acts on is called the enzyme’s substrate
The enzyme binds to its substrate, forming an enzyme-substrate complex
The active site is the region on the enzyme where the substrate binds
Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction
For the Cell Biology Video Closure of Hexokinase via Induced Fit, go to Animation and Video Files.
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55. Enzyme-substrate complex
Figure 8.14
Substrate
Active site
Figure 8.14 Induced fit between an enzyme and its substrate.
Enzyme
Enzyme-substrate complex
(a)
(b) 55

56. Catalysis in the Enzyme’s Active Site
In an enzymatic reaction, the substrate binds to the active site of the enzyme
The active site can lower an EA barrier by
Orienting substrates correctly
Straining substrate bonds
Providing a favorable microenvironment
Covalently bonding to the substrate
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57. Substrates enter active site.
Figure 1
Substrates enter active site.
Substrates are held in active site by weak interactions. 2
Substrates
Enzyme-substrate complex
Active site
Figure 8.15 The active site and catalytic cycle of an enzyme.
Enzyme 57

58. Substrates enter active site.
Figure 1
Substrates enter active site.
Substrates are held in active site by weak interactions. 2
Substrates
Enzyme-substrate complex
Active site can lower EA and speed up a reaction. 3
Active site
Figure 8.15 The active site and catalytic cycle of an enzyme.
Enzyme
Substrates are converted to products. 4 58

59. Substrates enter active site.
Figure 1
Substrates enter active site.
Substrates are held in active site by weak interactions. 2
Substrates
Enzyme-substrate complex
Active site can lower EA and speed up a reaction. 3
Active site is available for two new substrate molecules. 6
Figure 8.15 The active site and catalytic cycle of an enzyme.
Enzyme 5
Products are released.
Substrates are converted to products. 4
Products 59

60. Effects of Local Conditions on Enzyme Activity
An enzyme’s activity can be affected by
General environmental factors, such as temperature and pH
Chemicals that specifically influence the enzyme
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61. Effects of Temperature and pH
Each enzyme has an optimal temperature in which it can function
Each enzyme has an optimal pH in which it can function
Optimal conditions favor the most active shape for the enzyme molecule
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62. Optimal temperature for typical human enzyme (37°C)
Figure 8.16
Optimal temperature for typical human enzyme (37°C)
Optimal temperature for enzyme of thermophilic (heat-tolerant) bacteria (77°C)
Rate of reaction 20 40 60 80
100
120
Temperature (°C)
(a) Optimal temperature for two enzymes
Optimal pH for pepsin (stomach enzyme)
Optimal pH for trypsin (intestinal enzyme)
Figure 8.16 Environmental factors affecting enzyme activity.
Rate of reaction 1 2 3 4 5 6 7 8 9 10 pH
(b) Optimal pH for two enzymes 62

63. Optimal temperature for typical human enzyme (37°C)
Figure 8.16a
Optimal temperature for typical human enzyme (37°C)
Optimal temperature for enzyme of thermophilic (heat-tolerant) bacteria (77°C)
Rate of reaction
Figure 8.16 Environmental factors affecting enzyme activity. 20 40 60 80
100
120
Temperature (°C)
(a) Optimal temperature for two enzymes 63

64. Optimal pH for pepsin (stomach enzyme)
Figure 8.16b
Optimal pH for pepsin (stomach enzyme)
Optimal pH for trypsin (intestinal enzyme)
Rate of reaction
Figure 8.16 Environmental factors affecting enzyme activity. 1 2 3 4 5 6 7 8 9 10 pH
(b) Optimal pH for two enzymes 64

65. Cofactors Cofactors are nonprotein enzyme helpers
Cofactors may be inorganic (such as a metal in ionic form) or organic
An organic cofactor is called a coenzyme
Coenzymes include vitamins
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66. Enzyme Inhibitors
Competitive inhibitors bind to the active site of an enzyme, competing with the substrate
Noncompetitive inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
Examples of inhibitors include toxins, poisons, pesticides, and antibiotics
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67. (b) Competitive inhibition (c) Noncompetitive inhibition
Figure 8.17
(a) Normal binding
(b) Competitive inhibition
(c) Noncompetitive inhibition
Substrate
Active site
Competitive inhibitor
Enzyme
Figure 8.17 Inhibition of enzyme activity.
Noncompetitive inhibitor 67

68. The Evolution of Enzymes
Enzymes are proteins encoded by genes
Changes (mutations) in genes lead to changes in amino acid composition of an enzyme
Altered amino acids in enzymes may alter their substrate specificity
Under new environmental conditions a novel form of an enzyme might be favored
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69. Two changed amino acids were found near the active site. Active site
Figure 8.18
Two changed amino acids were found near the active site.
Active site
Figure 8.18 Mimicking evolution of an enzyme with a new function.
Two changed amino acids were found in the active site.
Two changed amino acids were found on the surface. 69

70. Concept 8.5: Regulation of enzyme activity helps control metabolism
Chemical chaos would result if a cell’s metabolic pathways were not tightly regulated
A cell does this by switching on or off the genes that encode specific enzymes or by regulating the activity of enzymes
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71. Allosteric Regulation of Enzymes
Allosteric regulation may either inhibit or stimulate an enzyme’s activity
Allosteric regulation occurs when a regulatory molecule binds to a protein at one site and affects the protein’s function at another site
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72. Allosteric Activation and Inhibition
Most allosterically regulated enzymes are made from polypeptide subunits
Each enzyme has active and inactive forms
The binding of an activator stabilizes the active form of the enzyme
The binding of an inhibitor stabilizes the inactive form of the enzyme
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73. Active site (one of four)
Figure 8.19
(a) Allosteric activators and inhibitors
(b) Cooperativity: another type of allosteric activation
Allosteric enzyme with four subunits
Active site (one of four)
Substrate
Regulatory site (one of four)
Activator
Inactive form
Stabilized active form
Active form
Stabilized active form
Oscillation
Figure 8.19 Allosteric regulation of enzyme activity.
Non- functional active site
Inhibitor
Inactive form
Stabilized inactive form 73

74. Active site (one of four)
Figure 8.19a
(a) Allosteric activators and inhibitors
Allosteric enzyme with four subunits
Active site (one of four)
Regulatory site (one of four)
Activator
Active form
Stabilized active form
Oscillation
Figure 8.19 Allosteric regulation of enzyme activity.
Nonfunctional active site
Inhibitor
Inactive form
Stabilized inactive form 74

75. (b) Cooperativity: another type of allosteric activation
Figure 8.19b
(b) Cooperativity: another type of allosteric activation
Substrate
Figure 8.19 Allosteric regulation of enzyme activity.
Inactive form
Stabilized active form 75

76. Cooperativity is a form of allosteric regulation that can amplify enzyme activity
One substrate molecule primes an enzyme to act on additional substrate molecules more readily
Cooperativity is allosteric because binding by a substrate to one active site affects catalysis in a different active site
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77. Identification of Allosteric Regulators
Allosteric regulators are attractive drug candidates for enzyme regulation because of their specificity
Inhibition of proteolytic enzymes called caspases may help management of inappropriate inflammatory responses
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78. EXPERIMENT RESULTS Figure 8.20 Caspase 1 Active site Substrate SH SH
Known active form
Active form can bind substrate
Allosteric binding site SH
Allosteric inhibitor
Known inactive form
Hypothesis: allosteric inhibitor locks enzyme in inactive form
Figure 8.20 Inquiry: Are there allosteric inhibitors of caspase enzymes?
RESULTS
Caspase 1
Inhibitor
Active form
Allosterically inhibited form
Inactive form 78

79. Active form can bind substrate
Figure 8.20a
EXPERIMENT
Caspase 1
Active site
Substrate SH SH
Known active form
Active form can bind substrate
Figure 8.20 Inquiry: Are there allosteric inhibitors of caspase enzymes?
Allosteric binding site SH
Allosteric inhibitor
Hypothesis: allosteric inhibitor locks enzyme in inactive form
Known inactive form 79

80. Allosterically inhibited form Inactive form
Figure 8.20b
RESULTS
Caspase 1
Inhibitor
Figure 8.20 Inquiry: Are there allosteric inhibitors of caspase enzymes?
Active form
Allosterically inhibited form
Inactive form 80

81. Feedback Inhibition
In feedback inhibition, the end product of a metabolic pathway shuts down the pathway
Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed
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82. Initial substrate (threonine)
Figure 8.21
Initial substrate (threonine)
Active site available
Threonine in active site
Enzyme 1 (threonine deaminase)
Isoleucine used up by cell
Intermediate A
Active site of enzyme 1 is no longer able to catalyze the conversion of threonine to intermediate A; pathway is switched off.
Feedback inhibition
Enzyme 2
Intermediate B
Enzyme 3
Intermediate C
Figure 8.21 Feedback inhibition in isoleucine synthesis.
Isoleucine binds to allosteric site.
Enzyme 4
Intermediate D
Enzyme 5
End product (isoleucine) 82

83. Specific Localization of Enzymes Within the Cell
Structures within the cell help bring order to metabolic pathways
Some enzymes act as structural components of membranes
In eukaryotic cells, some enzymes reside in specific organelles; for example, enzymes for cellular respiration are located in mitochondria
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84. Figure 8.22
Mitochondria
The matrix contains enzymes in solution that are involved in one stage of cellular respiration.
Enzymes for another stage of cellular respiration are embedded in the inner membrane.
Figure 8.22 Organelles and structural order in metabolism.
1 m 84

85. Figure 8.22a
Figure 8.22 Organelles and structural order in metabolism.
1 m 85

86. Course of reaction without enzyme EA without enzyme
Figure 8.UN03
Course of reaction without enzyme
EA without enzyme
EA with enzyme is lower
Reactants
Free energy
G is unaffected by enzyme
Course of reaction with enzyme
Figure 8.UN03 Summary figure, Concept 8.4
Products
Progress of the reaction 86

87. Figure 8.UN04
Figure 8.UN04 Appendix A: answer to Figure 8.12 legend question 87

88. Figure 8.UN05
Figure 8.UN05 Appendix A: answer to Figure 8.16 legend question 88

89. Figure 8.UN06
Figure 8.UN06 Appendix A: answer to Test Your Understanding, question 7 89

90. Figure 8.UN07
Figure 8.UN07 Appendix A: answer to Test Your Understanding, question 9 90

91. Figure 8.4
Figure 8.4 Order as a characteristic of life. 91

92. Figure 8.4a
Figure 8.4 Order as a characteristic of life. 92

93. Figure 8.4b
Figure 8.4 Order as a characteristic of life. 93

94. The evolution of more complex organisms does not violate the second law of thermodynamics
Entropy (disorder) may decrease in an organism, but the universe’s total entropy increases
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