1. Cellular Respiration: Obtaining Energy from Food
Chapter 6
Cellular Respiration: Obtaining Energy from Food

2. ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE
Animals depend on plants to convert the energy of sunlight to
chemical energy of sugars and
other organic molecules we consume as food.
Photosynthesis uses light energy from the sun to
power a chemical process and
make organic molecules.
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3. Producers and Consumers
Plants and other autotrophs (self-feeders)
make their own organic matter from inorganic nutrients.
Heterotrophs (other-feeders)
include humans and other animals that cannot make organic molecules from inorganic ones.
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Care should be taken to point out the need for mitochondria in plants when photosynthesis is not efficient or possible (such as during the night). 3

4. Producers and Consumers
Autotrophs are producers because ecosystems depend upon them for food.
Heterotrophs are consumers because they eat plants or other animals.
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5. Figure 6.1
Figure 6.1 Producer and consumer

6. Chemical Cycling between Photosynthesis and Cellular Respiration
The ingredients for photosynthesis are carbon dioxide (CO2) and water (H2O).
CO2 is obtained from the air by a plant’s leaves.
H2O is obtained from the damp soil by a plant’s roots.
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7. Chemical Cycling between Photosynthesis and Cellular Respiration
Chloroplasts in the cells of leaves use light energy to rearrange the atoms of CO2 and H2O, which produces
sugars (such as glucose),
other organic molecules, and
oxygen gas.
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8. Chemical Cycling between Photosynthesis and Cellular Respiration
Plant and animal cells perform cellular respiration, a chemical process that
primarily occurs in mitochondria,
harvests energy stored in organic molecules,
uses oxygen, and
generates ATP.
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9. Chemical Cycling between Photosynthesis and Cellular Respiration
The waste products of cellular respiration are
CO2 and H2O,
used in photosynthesis.
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10. Chemical Cycling between Photosynthesis and Cellular Respiration
Animals perform only cellular respiration.
Plants perform
photosynthesis and
cellular respiration.
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11. Chemical Cycling between Photosynthesis and Cellular Respiration
Plants usually make more organic molecules than they need for fuel. This surplus provides material that can be
used for the plant to grow or
stored as starch in potatoes.
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12. Photosynthesis Cellular respiration
Figure 6.2
Sunlight energy
enters ecosystem
Photosynthesis
C6H12O6
CO2 O2
H2O
Cellular respiration
drives cellular work
ATP
Heat energy exits
ecosystem
Figure 6.2 Energy flow and chemical cycling in ecosystems

13. CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY
Cellular respiration is
the main way that chemical energy is harvested from food and converted to ATP and
an aerobic process—it requires oxygen.
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14. CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY
Cellular respiration and breathing are closely related.
Cellular respiration requires a cell to exchange gases with its surroundings.
Cells take in oxygen gas.
Cells release waste carbon dioxide gas.
Breathing exchanges these same gases between the blood and outside air.
© 2013 Pearson Education, Inc.
Consider emphasizing the products, locations, and energy yields associated with glycolysis, the citric acid cycle, and electron transport before detailing the specifics of each reaction. Figure 6.6 can be especially helpful to provide physical orientation to these cellular processes.
Teaching Tips
As you relate the structure of the inner mitochondrial membrane to its functions, challenge the students to suggest an adaptive advantage of the many folds of this inner membrane. These folds greatly increase the membrane region available for the associated reactions. The production of NADH by glycolysis and the citric acid cycle, instead of just the direct production of ATP, can get confusing for students. Help students understand that NADH molecules have energy “value,” to be “cashed in” by the electron transport chain. The NADH can therefore be thought of as casino chips, accumulated along the way to be cashed in at the “electron transport” cashier.
The authors developed an analogy between the function of the inner mitochondrial membrane and a dam. A reservoir of hydrogen ions is built up between the mitochondrial membranes, like a dam holding back water. As the hydrogen ions move down their concentration gradient, they “spin” the ATP synthase, which helps generate ATP. In a dam, water rushing downhill turns giant turbines, which generate electricity. Students should be reminded that the ATP yield per glucose molecule of up to 32 ATP is only a potential. The complex chemistry of aerobic metabolism can only yield this amount under ideal conditions, when every substrate and enzyme is immediately available. Such circumstances may only rarely occur in a working cell. 14

15. O2 CO2 O2 CO2 Cellular respiration
Figure 6.3 O2
CO2
Breathing
Lungs O2
CO2
Muscle
cells
Cellular
respiration
Figure 6.3 How breathing is related to cellular respiration

16. The Simplified Equation for Cellular Respiration
A common fuel molecule for cellular respiration is glucose.
Cellular respiration can produce up to 32 ATP molecules for each glucose molecule consumed.
The overall equation for what happens to glucose during cellular respiration is
glucose & oxygen  CO2, H2O, & a release of energy.
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17. C6H12O6 6 O2 6 CO2 6 H2O ATP Glucose Oxygen Carbon dioxide Water
Figure 6.UN01
C6H12O6 6 O2 6
CO2 6
H2O
ATP
Glucose
Oxygen
Carbon
dioxide
Water
Energy
Figure 6.UN01 In-text figure, cellular respiration equation, p. 94

18. The Role of Oxygen in Cellular Respiration
During cellular respiration, hydrogen and its bonding electrons change partners from sugar to oxygen, forming water as a product.
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19. Redox Reactions
Chemical reactions that transfer electrons from one substance to another are called
oxidation-reduction reactions or
redox reactions for short.
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20. The loss of electrons during a redox reaction is oxidation.
Redox Reactions
The loss of electrons during a redox reaction is oxidation.
The acceptance of electrons during a redox reaction is reduction.
During cellular respiration
glucose is oxidized and
oxygen is reduced.
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21. Glucose loses electrons Oxygen gains electrons (and hydrogens)
Figure 6.UN02
Oxidation
Glucose loses electrons
(and hydrogens)
C6H12O6 6 O2 6
CO2 6
H2O
Glucose
Oxygen
Carbon
dioxide
Water
Reduction
Oxygen gains electrons (and hydrogens)
Figure 6.UN02 In-text figure, redox reaction, p. 95

22. Why does electron transfer to oxygen release energy?
Redox Reactions
Why does electron transfer to oxygen release energy?
When electrons move from glucose to oxygen, it is as though the electrons were falling.
This “fall” of electrons releases energy during cellular respiration.
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23. Cellular respiration is
Redox Reactions
Cellular respiration is
a controlled fall of electrons and
a stepwise cascade much like going down a staircase.
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24. NADH and Electron Transport Chains
The path that electrons take on their way down from glucose to oxygen involves many steps.
The first step is an electron acceptor called NAD+.
NAD is made by cells from niacin, a B vitamin.
The transfer of electrons from organic fuel to NAD+ reduces it to NADH.
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25. NADH and Electron Transport Chains
The rest of the path consists of an electron transport chain, which
involves a series of redox reactions and
ultimately leads to the production of large amounts of ATP.
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26. Electron transport chain
Figure 6.5 e e
Electrons from food e e
Stepwise release
of energy used
to make
NAD
NADH
ATP 2 H 2 e
Electron transport chain 2 e 2 H 2 1 O2
Hydrogen, electrons,
and oxygen combine
to produce water
H2O
Figure 6.5 The role of oxygen in harvesting food energy

27. H Electron transport chain 2 e H 2
Figure 6.5a
Stepwise release
of energy used
to make ATP
ATP 2 H 2 e
Electron
transport chain 2 e H 2 1 2 O2
Hydrogen, electrons, and oxygen
combine to produce water
H2O
Figure 6.5 The role of oxygen in harvesting food energy (detail)

28. An Overview of Cellular Respiration
Cellular respiration is an example of a metabolic pathway, which is a series of chemical reactions in cells.
All of the reactions involved in cellular respiration can be grouped into three main stages:
1. glycolysis,
2. the citric acid cycle, and
3. electron transport.
BioFlix Animation: Cellular Respiration
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29. Mitochondrion Cytoplasm Cytoplasm Animal cell Plant cell Cytoplasm
Figure 6.6
Mitochondrion
Cytoplasm
Cytoplasm
Animal cell
Plant cell
Cytoplasm
Mitochondrion
High-energy
electrons
via carrier
molecules
Glycolysis
Citric
Acid
Cycle 2
Pyruvic
acid
Electron
Transport
Glucose
ATP
ATP
ATP
Figure 6.6 A road map for cellular respiration

30. Cytoplasm Mitochondrion High-energy electrons via carrier molecules
Figure 6.6a
Cytoplasm
Mitochondrion
High-energy
electrons
via carrier
molecules
Glycolysis
Citric
Acid
Cycle 2
Pyruvic
acid
Electron
Transport
Glucose
ATP
ATP
ATP
Figure 6.6 A road map for cellular respiration (detail)

31. The Three Stages of Cellular Respiration
With the big-picture view of cellular respiration in mind, let’s examine the process in more detail.
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32. Stage 1: Glycolysis
A six-carbon glucose molecule is split in half to form two molecules of pyruvic acid.
These two molecules then donate high energy electrons to NAD+, forming NADH.
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33. Figure 6.7
INPUT
OUTPUT – –
NADH P P
2 ATP
NAD
2 ADP 2 3
2 ATP P
2 ADP P
2 Pyruvic acid 1 P P P 2 3
Glucose
2 ADP
NAD
2 ATP P – –
NADH
Energy investment phase
Energy harvest phase
Key
Carbon atom P
Phosphate group –
High-energy electron
Figure 6.7 Glycolysis

34. INPUT OUTPUT 2 Pyruvic acid Glucose Figure 6.7a
Figure 6.7 Glycolysis (part 1)

35. Energy investment phase
Figure 6.7b-1 P
2 ATP
2 ADP 1 P
Energy investment phase
Figure 6.7 Glycolysis (part 2, step 1)

36. Energy investment phase Energy harvest phase
Figure 6.7b-3 – –
NADH P P
2 ATP
NAD
2 ADP 2 3 P
2 ATP
2 ADP P 1 P P P 2 3
2 ADP
NAD
2 ATP P – –
NADH
Energy investment phase
Energy harvest phase
Figure 6.7 Glycolysis (part 2, step 3)

37. Stage 1: Glycolysis Glycolysis
uses two ATP molecules per glucose to split the six-carbon glucose and
makes four additional ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP.
Thus, glycolysis produces a net of two molecules of ATP per glucose molecule.
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38. Enzyme P ADP ATP P P Figure 6.8
Figure 6.8 ATP synthesis by direct phosphate transfer

39. Stage 2: The Citric Acid Cycle
In the citric acid cycle, pyruvic acid from glycolysis is first “groomed.”
Each pyruvic acid loses a carbon as CO2.
The remaining fuel molecule, with only two carbons left, is acetic acid.
Oxidation of the fuel generates NADH.
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40. Stage 2: The Citric Acid Cycle
Finally, each acetic acid is attached to a molecule called coenzyme A to form acetyl CoA.
The CoA escorts the acetic acid into the first reaction of the citric acid cycle.
The CoA is then stripped and recycled.
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41. INPUT OUTPUT 2 Oxidation of the fuel generates NADH (from glycolysis)
Figure 6.9
INPUT
OUTPUT 2
Oxidation of the fuel
generates NADH
(from
glycolysis)
(to citric
acid cycle) – –
NAD
NADH
CoA 1
Pyruvic acid
loses a carbon
as CO2 3
Acetic
acid
Acetic acid
attaches to
coenzyme A
Acetyl CoA
Pyruvic acid
CO2
Coenzyme A
Figure 6.9 The link between glycolysis and the citric acid cycle: the conversion of pyruvic acid to acetyl CoA

42. (from glycolysis) (to citric acid cycle)
Figure 6.9a
INPUT
OUTPUT
(from
glycolysis)
(to citric
acid cycle)
CoA
Acetyl CoA
Pyruvic acid
Figure 6.9 The link between glycolysis and the citric acid cycle: the conversion of pyruvic acid to acetyl CoA (part 1)

43. 2 Oxidation of the fuel generates NADH – – NAD NADH 1 3 Pyruvic acid
Figure 6.9b 2
Oxidation of the fuel
generates NADH – –
OUTPUT
NAD
NADH 1 3
Pyruvic acid
loses a carbon
as CO2
Acetic
acid
Acetic acid
attaches to
coenzyme A
CO2
Coenzyme A
Figure 6.9 The link between glycolysis and the citric acid cycle: the conversion of pyruvic acid to acetyl CoA (part 2)

44. Blast Animation: Harvesting Energy: Krebs Cycle
Stage 2: The Citric Acid Cycle
The citric acid cycle
extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2,
uses some of this energy to make ATP, and
forms NADH and FADH2.
Blast Animation: Harvesting Energy: Krebs Cycle
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45. INPUT OUTPUT 2 CO2 ATP – – – – FAD FADH2
Figure 6.10
INPUT
OUTPUT
Citric
acid 1
Acetic
acid 2
2 CO2 3
ADP  P
ATP
Citric
Acid
Cycle – –
3 NAD 4
3 NADH – –
FAD 5
FADH2 6
Acceptor
molecule
Figure 6.10 The citric acid cycle

46. Stage 3: Electron Transport
Electron transport releases the energy your cells need to make the most of their ATP.
The molecules of the electron transport chain are built into the inner membranes of mitochondria.
The chain
functions as a chemical machine, which
uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane, and
uses these ions to store potential energy.
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47. Stage 3: Electron Transport
When the hydrogen ions flow back through the membrane, they release energy.
The hydrogen ions flow through ATP synthase.
ATP synthase
takes the energy from this flow and
synthesizes ATP.
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48. Electron transport chain ATP synthase
Figure 6.11
Space
between
membranes H H H H H H H H
Electron
carrier H H H 3 H 5 H
Protein
complex
Inner
mitochondrial
membrane – –
FADH2
FAD H
Electron
flow 2 1 2 O2 2 H
H2O 6 – – 4
NADH
NAD
ADP P
ATP 1 H H H H H
Matrix
Electron transport chain
ATP synthase
Figure 6.11 How electron transport drives ATP synthase machines

49. Electron transport chain
Figure 6.11a
Space
between
membranes H H H H H H H H
Electron
carrier H H H 3 H 5 H
Protein
complex
Inner
mitochondrial
membrane – –
FADH2
FAD H
Electron
flow 2 1 2 O2 2 H
H2O 6 – – 4
NADH
NAD
ADP P
ATP 1 H H H H H
Matrix
Electron transport chain
ATP synthase
Figure 6.11 How electron transport drives ATP synthase machines (part 1)

50. Electron transport chain
Figure 6.11b
Space
between
membranes H H H H H H H
Electron
carrier H H H 3 H
Protein
complex
Inner
mitochondrial
membrane – –
FADH2
FAD H
Electron
flow 2 1 2 O2 2 H – – 4
NADH
NAD 1 H H H H
Matrix
Electron transport chain
Figure 6.11 How electron transport drives ATP synthase machines (part 2)

51. ATP synthase H H  H H H 5 H O2 6 H H2O 4 ADP P ATP H H 2
Figure 6.11c H H  H H H 5 H 1 2 O2 6 2 H
H2O 4
ADP P
ATP H H
ATP synthase
Figure 6.11 How electron transport drives ATP synthase machines (part 3)

52. Stage 3: Electron Transport
Cyanide is a deadly poison that
binds to one of the protein complexes in the electron transport chain,
prevents the passage of electrons to oxygen, and
stops the production of ATP.
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53. The Results of Cellular Respiration
Cellular respiration can generate up to 32 molecules of ATP per molecule of glucose.
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54. Cytoplasm Mitochondrion – – – – – – 6 NADH 2 NADH 2 NADH – – 2 FADH2
Figure 6.12
Cytoplasm
Mitochondrion – – – – – – 6
NADH 2
NADH 2
NADH – – 2
FADH2
Glycolysis 2
Pyruvic
acid 2
Acetyl
CoA
Citric
Acid
Cycle
Electron
Transport
Glucose
Maximum
per
glucose: 2
ATP 2
ATP
About
28 ATP
About
32 ATP
by direct
synthesis
by direct
synthesis
by ATP
synthase
Figure 6.12 A summary of ATP yield during cellular respiration

55. 2 Acetyl CoA 2 Pyruvic acid 2 ATP 2 ATP About 28 ATP
Figure 6.12a
Glycolysis 2
Acetyl
CoA 2
Pyruvic
acid
Citric
Acid
Cycle
Electron
Transport
Glucose 2
ATP 2
ATP
About
28 ATP
by direct
synthesis
by direct
synthesis
by ATP
synthase
Figure 6.12 A summary of ATP yield during cellular respiration (detail)

56. The Results of Cellular Respiration
In addition to glucose, cellular respiration can “burn”
diverse types of carbohydrates,
fats, and
proteins.
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57. Food Polysaccharides Fats Proteins Sugars Glycerol Fatty acids
Figure 6.13
Food
Polysaccharides
Fats
Proteins
Sugars
Glycerol
Fatty acids
Amino acids
Citric
Acid
Cycle
Acetyl
CoA
Glycolysis
Electron
Transport
ATP
Figure 6.13 Energy from food

58. FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY
Some of your cells can actually work for short periods without oxygen.
Fermentation is the anaerobic (without oxygen) harvest of food energy.
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Student Misconceptions and Concerns
Care should be taken to clarify the different possible products of fermentation in muscle cells and alcoholic fermentation used in the food and beverage industry.
Consider a simple demonstration mixing about equal portions of milk (skim or 2%) with some acid (vinegar will work). Notice the accumulation of strands of milk curd (protein) on the side of the container and stirring device.
Teaching Tips
1. The carbon dioxide released from fermentation also makes beer and champagne bubbly.
2. Dry wines are produced when the yeast cells use up all or most of the sugar available. Sweet wines result when the alcohol accumulates enough to inhibit fermentation before the sugar is depleted.
3. Exposing fermenting yeast to oxygen will slow or stop the process, because the yeast will switch back to aerobic respiration. When fermentation is rapid, the carbon dioxide produced drives away the immediate oxygen above the wine. However, as fermentation slows down, the wine must be sealed to prevent oxygen exposure and permit the fermentation process to finish. 58

59. Fermentation in Human Muscle Cells
After functioning anaerobically for about 15 seconds, muscle cells begin to generate ATP by the process of fermentation.
Fermentation relies on glycolysis to produce ATP.
Glycolysis
does not require oxygen and
produces two ATP molecules for each glucose broken down to pyruvic acid.
© 2013 Pearson Education, Inc. 59

60. Animation: Fermentation Overview
Fermentation in Human Muscle Cells
Pyruvic acid, produced by glycolysis,
is reduced by NADH,
producing NAD+, which
keeps glycolysis going.
In human muscle cells, lactic acid is a by-product.
Animation: Fermentation Overview
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61. Figure 6.14 Fermentation: producing lactic acid
INPUT
OUTPUT
2 ADP
2 ATP
2 P
Glycolysis – – – –
2 NAD
2 NADH
2 NADH
2 NAD
2 Pyruvic acid
2 H
Glucose
2 Lactic acid
Figure 6.14 Fermentation: producing lactic acid

62. INPUT OUTPUT 2 Lactic acid Glucose 2 ADP 2 ATP 2 P Glycolysis – – – –
Figure 6.14a
INPUT
OUTPUT
2 ADP
2 ATP
2 P
Glycolysis – – – –
2 NAD
2 NADH
2 NADH
2 NAD
2 Pyruvic acid 2 H
2 Lactic acid
Glucose
Figure 6.14 Fermentation: producing lactic acid (part 1)

63. The Process of Science: What Causes Muscle Burn?
Observation: Muscles produce lactic acid under anaerobic conditions.
Question: Does the buildup of lactic acid cause muscle fatigue?
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64. The Process of Science: What Causes Muscle Burn?
Hypothesis: The buildup of lactic acid would cause muscle activity to stop.
Experiment: Tested frog muscles under conditions when lactic acid
could and
could not diffuse away.
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65. diffusion of lactic acid diffusion of lactic acid;
Figure 6.15
Battery
Battery  –  –
Force
measured
Force
measured
Frog
muscle
stimulated
by electric
current
Solution prevents
diffusion of lactic acid
Solution allows
diffusion of lactic acid;
muscle can work for
twice as long
Figure 6.15 A. V. Hill’s 1929 apparatus for measuring muscle fatigue

66. The Process of Science: What Causes Muscle Burn?
Results: When lactic acid could diffuse away, performance improved greatly.
Conclusion: Lactic acid accumulation is the primary cause of failure in muscle tissue.
However, recent evidence suggests that the role of lactic acid in muscle function remains unclear.
© 2013 Pearson Education, Inc. 66

67. Fermentation in Microorganisms
Fermentation alone is able to sustain many types of microorganisms.
The lactic acid produced by microbes using fermentation is used to produce
cheese, sour cream, and yogurt,
soy sauce, pickles, and olives, and
sausage meat products.
© 2013 Pearson Education, Inc. 67

68. Fermentation in Microorganisms
Yeast is a microscopic fungus that
uses a different type of fermentation and
produces CO2 and ethyl alcohol instead of lactic acid.
This type of fermentation, called alcoholic fermentation, is used to produce
beer,
wine, and
breads.
© 2013 Pearson Education, Inc. 68

69. Figure 6.16 Fermentation: producing ethyl alcohol
INPUT
OUTPUT
2 ADP
2 ATP
 2 P
2 CO2 released
Glycolysis – – – –
2 NAD
2 NADH
2 NADH
2 NAD
2 Ethyl alcohol
2 Pyruvic
acid  2 H
Glucose
Figure 6.16 Fermentation: producing ethyl alcohol

70. INPUT OUTPUT 2 ADP 2 ATP  2 P 2 CO2 released Glycolysis 2 NAD 2 NADH
Figure 6.16a
INPUT
OUTPUT
2 ADP
2 ATP
 2 P
2 CO2 released
Glycolysis – – – –
2 NAD
2 NADH
2 NADH
2 NAD
2 Ethyl alcohol
2 Pyruvic
acid 2 H
Glucose
Figure 6.16 Fermentation: producing ethyl alcohol (part 1)

71. Figure 6.16b
Figure 6.16 Fermentation: producing ethyl alcohol (part 2)

72. Evolution Connection: Life before and after Oxygen
Glycolysis could be used by ancient bacteria to make ATP
when little oxygen was available, and
before organelles evolved.
Today, glycolysis
occurs in almost all organisms and
is a metabolic heirloom of the first stage in the breakdown of organic molecules.
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73. First eukaryotic organisms 2.2
Figure 6.17
Earth’s atmosphere
O2 present in
2.1
First eukaryotic organisms
2.2
Atmospheric oxygen reaches 10% of modern levels
2.7
Atmospheric oxygen
first appears
Billions of years ago
3.5
Oldest prokaryotic
fossils
4.5
Origin of Earth
Figure 6.17 A time line of oxygen and life on Earth

74. First eukaryotic organisms 2.2
Figure 6.17a
Earth’s atmosphere
O2 present in
2.1
First eukaryotic organisms
2.2
Atmospheric oxygen reaches 10% of modern levels
2.7
Atmospheric oxygen
first appears
Billions of years ago
3.5
Oldest prokaryotic
fossils
4.5
Origin of Earth
Figure 6.17 A time line of oxygen and life on Earth (part 1)

75. Figure 6.17b
Figure 6.17 A time line of oxygen and life on Earth (part 2)

76. Citric Acid Cycle Electron Transport
Figure 6.UN03
Citric
Acid
Cycle
Electron
Transport
Glycolysis
ATP
ATP
ATP
Figure 6.UN03 In-text figure, glycolysis, p. 97

77. Citric Acid Cycle Electron Transport
Figure 6.UN04
Citric
Acid
Cycle
Electron
Transport
Glycolysis
ATP
ATP
ATP
Figure 6.UN04 In-text figure, citric acid cycle, p. 98

78. Citric Acid Cycle Electron Transport
Figure 6.UN05
Citric
Acid
Cycle
Electron
Transport
Glycolysis
ATP
ATP
ATP
Figure 6.UN05 In-text figure, electron transport chain, p. 99

79. C6H12O6 Heat Sunlight O2 ATP Cellular respiration CO2 H2O
Figure 6.UN06
Heat
C6H12O6
Sunlight O2
ATP
Cellular
respiration
Photosynthesis
CO2
H2O
Figure 6.UN06 Summary of Key Concepts: Chemical Cycling between Photosynthesis and Cellular Respiration

80. C6H12O6  6 O2 6 CO2  6 H2O  Approx. 32 ATP
Figure 6.UN07
C6H12O6
 6 O2 6
CO2
 6
H2O
 Approx. 32
ATP
Figure 6.UN07 Summary of Key Concepts: The Simplified Equation for Cellular Respiration

81. Glucose loses electrons (and hydrogens)
Figure 6.UN08
Oxidation
Glucose loses electrons
(and hydrogens)
C6H12O6
CO2
ATP
Electrons
(and hydrogens) O2
H2O
Reduction
Oxygen gains
electrons (and
hydrogens)
Figure 6.UN08 Summary of Key Concepts: The Role of Oxygen in Cellular Respiration

82. Mitochondrion O2 – – – – – – 6 NADH 2 NADH 2 NADH – – 2 FADH2
Figure 6.UN09
Mitochondrion O2 – – – – – – 6
NADH 2
NADH 2
NADH – – 2
FADH2
Glycolysis 2
Acetyl
CoA
Citric
Acid
Cycle 2
Pyruvic
acid
Electron
Transport
Glucose 2
CO2 4
CO2
H2O
About
28 ATP 2
ATP
by direct
synthesis
by direct
synthesis 2
ATP
by ATP
synthase
About
32 ATP
Figure 6.UN09 Summary of Key Concepts: An Overview of Cellular Respiration