1. Cellular Respiration and Fermentation7
Cellular Respiration and Fermentation

2. Overview: Life Is Work
Living cells require energy from outside sources
Some animals, such as the giraffe, obtain energy by eating plants, and some animals feed on other organisms that eat plants.
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3. Figure 7.1
Figure 7.1 How do these leaves power the work of life for this giraffe? 3

4. Energy flows into an ecosystem as sunlight and leaves as heat
Photosynthesis generates O2 and organic molecules, which are used as fuel for cellular respiration
Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work.
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5. Video: Carbon Cycle

6. Light energy ECOSYSTEM Photosynthesis in chloroplasts Organic
Figure 7.2
Light
energy
ECOSYSTEM
Photosynthesis
in chloroplasts
Organic
molecules
CO2  H2O
 O2
Cellular respiration
in mitochondria
Figure 7.2 Energy flow and chemical recycling in ecosystems
ATP powers
most cellular work
ATP
Heat
energy 6

7. Concept 7.1: Catabolic pathways yield energy by oxidizing organic fuels
Several processes are central to cellular respiration and related pathways.
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8. Catabolic Pathways and Production of ATP
The breakdown of organic molecules is exergonic
Fermentation is a partial degradation of sugars that occurs without O2
Aerobic respiration consumes organic molecules and O2 and yields ATP
Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2.
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9. C6H12O6  6 O2  6 CO2  6 H2O  Energy (ATP  heat).
Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration
Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose
C6H12O6  6 O2  6 CO2  6 H2O  Energy (ATP  heat).
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10. Redox Reactions: Oxidation and Reduction
The transfer of electrons during chemical reactions releases energy stored in organic molecules
This released energy is ultimately used to synthesize ATP.
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11. The Principle of Redox
Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions
In oxidation, a substance loses electrons, or is oxidized
In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced).
Mnemonic: OIL- RIG
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12. The electron donor is called the reducing agent
The electron acceptor is called the oxidizing agent
Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds
An example is the reaction between methane and O2.
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13. Reactants Products becomes oxidized becomes reduced Methane (reducing
Figure 7.3
Reactants
Products
becomes oxidized
becomes reduced
Figure 7.3 Methane combustion as an energy-yielding redox reaction
Methane
(reducing
agent)
Oxygen
(oxidizing
agent)
Carbon dioxide
Water 13

14. Redox reactions that move electrons closer to electronegative atoms, like oxygen, release chemical energy that can be put to work.
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15. Oxidation of Organic Fuel Molecules During Cellular Respiration
During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced
Organic molecules with an abundance of hydrogen, like carbohydrates and fats, are excellent fuels
As hydrogen (with its electron) is transferred to oxygen, energy is released that can be used in ATP sythesis.
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16. becomes oxidized becomes reduced
Figure 7.UN03
becomes oxidized
becomes reduced
Figure 7.UN03 In-text figure, cellular respiration redox reaction, p. 137 16

17. Stepwise Energy Harvest via NAD+ and the Electron Transport Chain
In cellular respiration, glucose and other organic molecules are broken down in a series of steps
Electrons from organic compounds are usually first transferred to NAD, a coenzyme
As an electron acceptor, NAD functions as an oxidizing agent during cellular respiration
Each NADH (the reduced form of NAD) represents stored energy that is tapped to synthesize ATP.
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18. NAD Nicotinamide (oxidized form) Figure 7.4a
Figure 7.4a NAD+ as an electron shuttle (part 1: NAD+ structure) 18

19. 2 e−  2 H 2 e−  H H NADH Dehydrogenase Reduction of NAD   2[H]
Figure 7.4b
2 e−  2 H
2 e−  H H
NADH
Dehydrogenase
Reduction of NAD
 2[H]
(from food)  H
Oxidation of NADH
Nicotinamide
(reduced form)
Figure 7.4b NAD+ as an electron shuttle (part 2: NAD+ reaction) 19

20. NADH passes the electrons to the electron transport chain
Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction
O2 pulls electrons down the chain in an energy-yielding tumble
The energy yielded is used to regenerate ATP.
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21. (a) Uncontrolled reaction (b) Cellular respiration
Figure 7.5
H2  O2
2 H  O2
Controlled
release of
energy
2 H  2 e−
ATP
ATP
Explosive
release
Electron transport
chain
Free energy, G
Free energy, G
ATP
2 e−
Figure 7.5 An introduction to electron transport chains O2
2 H
H2O
H2O
(a) Uncontrolled reaction
(b) Cellular respiration 21

22. The Stages of Cellular Respiration: A Preview
Harvesting of energy from glucose has three stages
Glycolysis (breaks down glucose into two molecules of pyruvate)
Pyruvate oxidation and the citric acid cycle (completes the breakdown of glucose)
Oxidative phosphorylation (accounts for most of the ATP synthesis).
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23. Animation: Cellular Respiration
Right click slide / Select play

24. Glycolysis (color-coded teal throughout the chapter)
Figure 7.UN05 1.
Glycolysis (color-coded teal throughout the chapter) 2.
Pyruvate oxidation and the citric acid cycle
(color-coded salmon) 3.
Oxidative phosphorylation: electron transport and
chemiosmosis (color-coded violet)
Figure 7.UN05 In-text figure, color code for stages of cellular respiration, p. 139 24

25. Electrons via NADH Glycolysis Glucose Pyruvate CYTOSOL MITOCHONDRION
Figure 7.6-1
Electrons
via NADH
Glycolysis
Glucose
Pyruvate
CYTOSOL
MITOCHONDRION
Figure An overview of cellular respiration (step 1)
ATP
Substrate-level 25

26. Electrons via NADH and FADH2 Electrons via NADH Pyruvate oxidation
Figure 7.6-2
Electrons
via NADH and
FADH2
Electrons
via NADH
Pyruvate
oxidation
Glycolysis
Citric
acid
cycle
Glucose
Pyruvate
Acetyl CoA
CYTOSOL
MITOCHONDRION
Figure An overview of cellular respiration (step 2)
ATP
ATP
Substrate-level
Substrate-level 26

27. Electrons via NADH and FADH2 Electrons via NADH Oxidative
Figure 7.6-3
Electrons
via NADH and
FADH2
Electrons
via NADH
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Pyruvate
oxidation
Glycolysis
Citric
acid
cycle
Glucose
Pyruvate
Acetyl CoA
CYTOSOL
MITOCHONDRION
Figure An overview of cellular respiration (step 3)
ATP
ATP
ATP
Substrate-level
Substrate-level
Oxidative 27

28. The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions.
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29. Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration
A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation
For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP.
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30. Enzyme Enzyme ADP Substrate  ATP Product
Figure 7.7
Enzyme
Enzyme
ADP P
Substrate 
ATP
Figure 7.7 Substrate-level phosphorylation
Product 30

31. Concept 7.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
Glycolysis (“sugar splitting”) breaks down glucose into two molecules of pyruvate
Glycolysis occurs in the cytoplasm and has two major phases
Energy investment phase
Energy payoff phase
Glycolysis occurs whether or not O2 is present.
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32. Citric acid cycle Oxidative phosphorylation Pyruvate oxidation
Figure 7.UN06
Citric
acid
cycle
Oxidative
phosphorylation
Pyruvate
oxidation
Glycolysis
Figure 7.UN06 In-text figure, mini-map, glycolysis, p. 140
ATP
ATP
ATP 32

33. Energy Investment Phase
Figure 7.8
Energy Investment Phase
Glucose
2 ADP  2 P
2 ATP
used
Energy Payoff Phase
4 ADP  4 P
4 ATP
formed
2 NAD  4 e−  4 H
2 NADH
 2 H
Figure 7.8 The energy input and output of glycolysis
2 Pyruvate  2 H2O
Net
Glucose
2 Pyruvate  2 H2O
4 ATP formed − 2 ATP used
2 ATP
2 NAD  4 e−  4 H
2 NADH  2 H 33

34. Glycolysis: Energy Investment Phase
Figure 7.9a
Glycolysis: Energy Investment Phase
Glyceraldehyde
3-phosphate (G3P)
ATP
Glucose
6-phosphate
Fructose
6-phosphate
ATP
Fructose
1,6-bisphosphate
Glucose
ADP
ADP
Isomerase 5
Hexokinase
Phosphogluco-
isomerase
Phospho-
fructokinase
Aldolase
Dihydroxyacetone
phosphate (DHAP) 1 4 2 3
Figure 7.9a A closer look at glycolysis (part 1: investment phase) 34

35. Glycolysis: Energy Payoff Phase
Figure 7.9b
Glycolysis: Energy Payoff Phase
2 ATP
2 ATP
2 NADH
2 H2O
Glyceraldehyde
3-phosphate (G3P)
2 ADP
2 NAD
 2 H
2 ADP 2 2 2 2 2
Triose
phosphate
dehydrogenase
Phospho-
glycerokinase
Phospho-
glyceromutase
Enolase
Pyruvate
kinase 2 P i 9
1,3-Bisphospho-
glycerate 7
3-Phospho-
glycerate 8
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP) 10
Pyruvate 6
Figure 7.9b A closer look at glycolysis (part 2: payoff phase) 35

36. Glycolysis: Energy Payoff Phase
Figure 7.9bb-3
Glycolysis: Energy Payoff Phase
2 ATP
2 H2O
2 ADP 2 2 2 2
Phospho-
glyceromutase
Enolase
Pyruvate
kinase 9
3-Phospho-
glycerate 8
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP) 10
Pyruvate
Figure 7.9bb-3 A closer look at glycolysis (part 2b, step 3) 36

37. Concept 7.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules
In the presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells), where the oxidation of glucose is completed
Before the citric acid cycle can begin, pyruvate must be converted to acetyl coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle.
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38. Citric acid cycle Oxidative phosphorylation Pyruvate oxidation
Figure 7.UN07
Citric
acid
cycle
Oxidative
phosphorylation
Pyruvate
oxidation
Glycolysis
Figure 7.UN07 In-text figure, mini-map, pyruvate oxidation, p. 142
ATP
ATP
ATP 38

39. Citric acid cycle Figure 7.10 Pyruvate (from glycolysis,
2 molecules per glucose)
CYTOSOL
CO2
NAD
CoA
NADH
 H
Acetyl CoA
MITOCHONDRION
CoA
CoA
Citric
acid
cycle
Figure 7.10 An overview of pyruvate oxidation and the citric acid cycle 2
CO2
FADH2
3 NAD
FAD 3
NADH
 3 H
ADP  P i
ATP 39

40. The citric acid cycle, also called the Krebs cycle, completes the breakdown of pyruvate to CO2
The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn.
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41. Citric acid cycle Oxidative phosphorylation Pyruvate oxidation
Figure 7.UN08
Citric
acid
cycle
Oxidative
phosphorylation
Pyruvate
oxidation
Glycolysis
Figure 7.UN08 In-text figure, mini-map, citric acid cycle, p. 143
ATP
ATP
ATP 41

42. Citric acid cycle Figure 7.11-1 Acetyl CoA 1 Oxaloacetate 2 Citrate
CoA-SH 1
H2O
Oxaloacetate 2
Citrate
Isocitrate
Citric
acid
cycle
Figure A closer look at the citric acid cycle (steps 1-2) 42

43. Citric acid cycle Figure 7.11-2 Acetyl CoA 1 Oxaloacetate 2 Citrate
CoA-SH 1
H2O
Oxaloacetate 2
Citrate
Isocitrate
NAD
Citric
acid
cycle 3
NADH
 H
CO2
-Ketoglutarate
Figure A closer look at the citric acid cycle (step 3) 43

44. Citric acid cycle Figure 7.11-3 Acetyl CoA 1 Oxaloacetate 2 Citrate
CoA-SH 1
H2O
Oxaloacetate 2
Citrate
Isocitrate
NAD
Citric
acid
cycle 3
NADH
 H
CO2
CoA-SH
-Ketoglutarate
Figure A closer look at the citric acid cycle (step 4) 4
CO2
NAD
NADH
Succinyl
CoA
 H 44

45. Citric acid cycle Figure 7.11-4 Acetyl CoA 1 Oxaloacetate 2 Citrate
CoA-SH 1
H2O
Oxaloacetate 2
Citrate
Isocitrate
NAD
Citric
acid
cycle 3
NADH
 H
CO2
CoA-SH
-Ketoglutarate
Figure A closer look at the citric acid cycle (step 5) 4
CoA-SH 5
CO2
NAD
Succinate P
NADH i
GTP
GDP
Succinyl
CoA
 H
ADP
ATP formation
ATP 45

46. Citric acid cycle Figure 7.11-5 Acetyl CoA 1 Oxaloacetate 2 Malate
CoA-SH 1
H2O
Oxaloacetate 2
Malate
Citrate
Isocitrate
NAD
Citric
acid
cycle 3
NADH 7
 H
H2O
CO2
Fumarate
CoA-SH
-Ketoglutarate
Figure A closer look at the citric acid cycle (steps 6-7) 6 4
CoA-SH 5
FADH2
CO2
NAD
FAD
Succinate P
NADH i
GTP
GDP
Succinyl
CoA
 H
ADP
ATP formation
ATP 46

47. Citric acid cycle Figure 7.11-6 Acetyl CoA 1 Oxaloacetate 8 2 Malate
CoA-SH
NADH 1
 H
H2O
NAD
Oxaloacetate 8 2
Malate
Citrate
Isocitrate
NAD
Citric
acid
cycle 3
NADH 7
 H
H2O
CO2
Fumarate
CoA-SH
-Ketoglutarate
Figure A closer look at the citric acid cycle (step 8) 6 4
CoA-SH 5
FADH2
CO2
NAD
FAD
Succinate P
NADH i
GTP
GDP
Succinyl
CoA
 H
ADP
ATP formation
ATP 47

48. The citric acid cycle has eight steps, each catalyzed by a specific enzyme
The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate
The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle
The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain.
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49. Concept 7.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis
Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food
These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation.
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50. The Pathway of Electron Transport
The electron transport chain is in the inner membrane (cristae) of the mitochondrion
Most of the chain’s components are proteins, which exist in multiprotein complexes
The carriers alternate reduced and oxidized states as they accept and donate electrons
Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O.
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51. Oxidative phosphorylation: electron transport and chemiosmosis Citric
Figure 7.UN09
Oxidative
phosphorylation:
electron transport
and chemiosmosis
Citric
acid
cycle
Pyruvate
oxidation
Glycolysis
Figure 7.UN09 In-text figure, mini-map, oxidative phosphorylation, p. 144
ATP
ATP
ATP 51

52. Free energy (G) relative to O2 (kcal/mol)
Figure 7.12a
NADH 50 2 e−
NAD
FADH2 2 e−
FAD
Multiprotein
complexes I 40
FMN II
Fe•S
Fe•S Q
III
Cyt b
Free energy (G) relative to O2 (kcal/mol)
Fe•S 30
Cyt c1 IV
Cyt c
Figure 7.12a Free-energy change during electron transport (part 1)
Cyt a
Cyt a3 20 2 e− 10 52

53. Free energy (G) relative to O2 (kcal/mol)
Figure 7.12b 30
Cyt c1 IV
Cyt c
Cyt a
Cyt a3 20
Free energy (G) relative to O2 (kcal/mol) 2 e− 10
(originally from
NADH or FADH2)
Figure 7.12b Free-energy change during electron transport (part 2)
2 H  ½ O2
H2O 53

54. The electron transport chain generates no ATP directly
Electrons are transferred from NADH or FADH2 to the electron transport chain
Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2
The electron transport chain generates no ATP directly
It breaks the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts.
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55. Chemiosmosis: The Energy-Coupling Mechanism
Electron transfer in the electron transport chain causes proteins to pump H from the mitochondrial matrix to the intermembrane space
H then moves back across the membrane, passing through the protein complex, ATP synthase
ATP synthase uses the exergonic flow of H to drive phosphorylation of ATP
This is an example of chemiosmosis, the use of energy in a H gradient to drive cellular work.
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56. H INTERMEMBRANE SPACE Stator Rotor Internal rod Catalytic knob ADP 
Figure 7.13 H
INTERMEMBRANE SPACE
Stator
Rotor
Internal rod
Catalytic knob
Figure 7.13 ATP synthase, a molecular mill
ADP  P
ATP
MITOCHONDRIAL MATRIX i 56

57. How do we know the structure of ATP synthase?
10 pts. e.c. – Read Mechanically driven ATP synthase by F1-ATPase- source: Nature. Answer questions 1-16.

58. The energy stored in a H gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis
The H gradient is referred to as a proton-motive force, emphasizing its capacity to do work.
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59. Oxidative phosphorylation: electron transport and chemiosmosis Citric
Figure 7.UN09
Oxidative
phosphorylation:
electron transport
and chemiosmosis
Citric
acid
cycle
Pyruvate
oxidation
Glycolysis
Figure 7.UN09 In-text figure, mini-map, oxidative phosphorylation, p. 146
ATP
ATP
ATP 59

60. Electron transport chain Oxidative phosphorylation
Figure 7.14 H H
Protein
complex
of electron
carriers H H
Cyt c IV Q
III I
ATP
synthase II
2 H  ½ O2
H2O
FADH2
FAD
NADH
NAD
Figure 7.14 Chemiosmosis couples the electron transport chain to ATP synthesis
ADP  P
ATP i
(carrying electrons
from food) H 1
Electron transport chain 2
Chemiosmosis
Oxidative phosphorylation 60

61. Electron transport chain
Figure 7.14a H H
Protein
complex
of electron
carriers H
Cyt c IV Q
III I II
2 H  ½ O2
H2O
FADH2
FAD
Figure 7.14a Chemiosmosis couples the electron transport chain to ATP synthesis (part 1: electron transport chain)
NAD
NADH
(carrying electrons
from food) 1
Electron transport chain 61

62. 2 ATP synthase Chemiosmosis H H ADP  ATP i P Figure 7.14b
Figure 7.14b Chemiosmosis couples the electron transport chain to ATP synthesis (part 2: chemiosmosis)
ADP  P
ATP i H 2
Chemiosmosis 62

63. An Accounting of ATP Production by Cellular Respiration
During cellular respiration, most energy flows in the following sequence:
glucose  NADH  electron transport chain  proton-motive force  ATP
About 34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 32 ATP
There are several reasons why the number of ATP molecules is not known exactly.
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64. Electron shuttles span membrane MITOCHONDRION 2 NADH CYTOSOL or
Figure 7.15
Electron shuttles
span membrane
MITOCHONDRION
2 NADH
CYTOSOL or
2 FADH2
2 NADH
2 NADH
6 NADH
2 FADH2
Glycolysis
Pyruvate
oxidation
2 Acetyl CoA
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Citric
acid
cycle 2
Pyruvate
Glucose
 2 ATP
Figure 7.15 ATP yield per molecule of glucose at each stage of cellular respiration
 2 ATP
 about 26 or 28 ATP
About
30 or 32 ATP
Maximum per glucose: 64

65. Concept 7.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen
Most cellular respiration requires O2 to produce ATP
Without O2, the electron transport chain will cease to operate
In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP.
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66. Anaerobic respiration uses an electron transport chain with a final electron acceptor other than O2, for example, sulfate
Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP.
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67. Types of Fermentation
Fermentation consists of glycolysis plus reactions that regenerate NAD, which can be reused by glycolysis
Two common types are alcohol fermentation and lactic acid fermentation.
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68. In alcohol fermentation, pyruvate is converted to ethanol in two steps
The first step releases CO2 from pyruvate, and the second step reduces acetaldehyde to ethanol
Alcohol fermentation by yeast is used in brewing, winemaking, and baking.
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69. Animation: Fermentation Overview
Right click slide / Select play

70. (a) Alcohol fermentation (b) Lactic acid fermentation
Figure 7.16
2 ADP  2 P
2 ADP  2 i
2 ATP P i
2 ATP
Glucose
Glycolysis
Glucose
Glycolysis
2 Pyruvate
2 NAD
2 NADH 2
CO2
2 NAD
2 NADH
 2 H
 2 H
2 Pyruvate
Figure 7.16 Fermentation
2 Ethanol
2 Acetaldehyde
2 Lactate
(a) Alcohol fermentation
(b) Lactic acid fermentation 70

71. (a) Alcohol fermentation
Figure 7.16a
2 ADP  2 P
2 ATP i
Glucose
Glycolysis
2 Pyruvate
2 NAD
2 NADH 2
CO2
 2 H
Figure 7.16a Fermentation (part 1: alcohol)
2 Acetaldehyde
2 Ethanol
(a) Alcohol fermentation 71

72. (b) Lactic acid fermentation
Figure 7.16b
2 ADP  2 P
2 ATP i
Glucose
Glycolysis
2 NAD
2 NADH
 2 H
2 Pyruvate
Figure 7.16b Fermentation (part 2: lactic acid)
2 Lactate
(b) Lactic acid fermentation 72

73. In lactic acid fermentation, pyruvate is reduced by NADH, forming lactate as an end product, with no release of CO2
Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt
Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce.
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74. Comparing Fermentation with Anaerobic and Aerobic Respiration
All use glycolysis (net ATP  2) to oxidize glucose and harvest chemical energy of food
In all three, NAD is the oxidizing agent that accepts electrons during glycolysis
The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration
Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule.
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75. Obligate anaerobes carry out only fermentation or anaerobic respiration and cannot survive in the presence of O2
Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration
In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes.
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76. Ethanol, lactate, or other products Citric acid cycle
Figure 7.17
Glucose
Glycolysis
CYTOSOL
Pyruvate
No O2 present:
Fermentation
O2 present:
Aerobic cellular
respiration
MITOCHONDRION
Ethanol,
lactate, or
other products
Acetyl CoA
Figure 7.17 Pyruvate as a key juncture in catabolism
Citric
acid
cycle 76

77. The Evolutionary Significance of Glycolysis
Ancient prokaryotes are thought to have used glycolysis long before there was oxygen in the atmosphere
Very little O2 was available in the atmosphere until about 2.7 billion years ago, so early prokaryotes likely used only glycolysis to generate ATP
Glycolysis is a very ancient process.
Assignment: Focused notes- discover article- include 3- higher-level questions to share on Friday.
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78. Concept 7.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways
Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways.
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79. The Versatility of Catabolism
Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration
Glycolysis accepts a wide range of carbohydrates
Proteins must be digested to amino acids and amino groups must be removed before amino acids can feed glycolysis or the citric acid cycle.
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80. Fats are digested to glycerol (used in glycolysis) and fatty acids
Fatty acids are broken down by beta oxidation and yield acetyl CoA
An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate.
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81. Amino acids Fatty acids
Figure
Proteins
Carbohydrates
Fats
Amino
acids
Sugars
Glycerol
Fatty
acids
Figure The catabolism of various molecules from food (step 1) 81

82. Amino acids Fatty acids
Figure
Proteins
Carbohydrates
Fats
Amino
acids
Sugars
Glycerol
Fatty
acids
Glycolysis
Glucose
Glyceraldehyde 3- P
NH3
Pyruvate
Figure The catabolism of various molecules from food (step 2) 82

83. Amino acids Fatty acids
Figure
Proteins
Carbohydrates
Fats
Amino
acids
Sugars
Glycerol
Fatty
acids
Glycolysis
Glucose
Glyceraldehyde 3- P
NH3
Pyruvate
Figure The catabolism of various molecules from food (step 3)
Acetyl CoA 83

84. Amino acids Fatty acids Citric acid cycle
Figure
Proteins
Carbohydrates
Fats
Amino
acids
Sugars
Glycerol
Fatty
acids
Glycolysis
Glucose
Glyceraldehyde 3- P
NH3
Pyruvate
Figure The catabolism of various molecules from food (step 4)
Acetyl CoA
Citric
acid
cycle 84

85. Amino acids Fatty acids Citric acid cycle Oxidative phosphorylation
Figure
Proteins
Carbohydrates
Fats
Amino
acids
Sugars
Glycerol
Fatty
acids
Glycolysis
Glucose
Glyceraldehyde 3- P
NH3
Pyruvate
Figure The catabolism of various molecules from food (step 5)
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation 85

86. INTER- MEMBRANE SPACE H MITO- ATP CHONDRIAL synthase MATRIX ADP  ATP
Figure 7.UN13b
INTER-
MEMBRANE
SPACE H
MITO-
CHONDRIAL
MATRIX
ATP
synthase
Figure 7.UN13b Summary of key concepts: oxidative phosphorylation (part 2)
ADP  P H
ATP i 86