1. Cellular Respiration and Fermentation7
Cellular Respiration and Fermentation

2. 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
The net energy yield is 2 ATP plus 2 NADH per glucose molecule
Glycolysis occurs whether or not O2 is present
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3. CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE
Figure 7.UN06
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYL-
ATION
PYRUVATE
OXIDATION
GLYCOLYSIS
Figure 7.UN06 In-text figure, mini-map, glycolysis, p. 147
ATP
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4. Energy Investment Phase
Figure 7.8
Energy Investment Phase
Glucose 2
ATP used
2 ADP + 2 P
Energy Payoff Phase
4 ADP P 4
ATP formed
2 NAD 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 e + 4 H+
2 NADH + 2 H+
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5. GLYCOLYSIS: Energy Investment Phase
Figure 7.9-1
GLYCOLYSIS: Energy Investment Phase
Glyceraldehyde
3-phosphate (G3P)
ATP
Glucose
6-phosphate
Fructose
6-phosphate
ATP
Fructose
1,6-bisphosphate
Glucose
ADP
ADP
Isomerase
Hexokinase
Phosphogluco-
isomerase
Phospho-
fructokinase
Aldolase
Dihydroxyacetone
phosphate (DHAP)
Figure A closer look at glycolysis (part 1: investment phase)
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6. GLYCOLYSIS: Energy Investment Phase
Figure 7.9-1a-s1
GLYCOLYSIS: Energy Investment Phase
Glucose
Figure 7.9-1a-s1 A closer look at glycolysis (part 1a, step 1)
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7. GLYCOLYSIS: Energy Investment Phase
Figure 7.9-1a-s2
GLYCOLYSIS: Energy Investment Phase
ATP
Glucose
6-phosphate
Glucose
ADP
Hexokinase
Figure 7.9-1a-s2 A closer look at glycolysis (part 1a, step 2)
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8. GLYCOLYSIS: Energy Investment Phase
Figure 7.9-1a-s3
GLYCOLYSIS: Energy Investment Phase
ATP
Glucose
6-phosphate
Fructose
6-phosphate
Glucose
ADP
Hexokinase
Phosphogluco-
isomerase
Figure 7.9-1a-s3 A closer look at glycolysis (part 1a, step 3)
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9. GLYCOLYSIS: Energy Investment Phase
Figure 7.9-1b-s1
GLYCOLYSIS: Energy Investment Phase
Fructose
6-phosphate
Figure 7.9-1b-s1 A closer look at glycolysis (part 1b, step 1)
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10. GLYCOLYSIS: Energy Investment Phase
Figure 7.9-1b-s2
GLYCOLYSIS: Energy Investment Phase
Fructose
6-phosphate
Fructose
1,6-bisphosphate
ATP
ADP
Phospho-
fructokinase
Figure 7.9-1b-s2 A closer look at glycolysis (part 1b, step 2)
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11. GLYCOLYSIS: Energy Investment Phase
Figure 7.9-1b-s3
GLYCOLYSIS: Energy Investment Phase
Glyceraldehyde
3-phosphate (G3P)
Fructose
6-phosphate
Fructose
1,6-bisphosphate
ATP
ADP
Isomerase
Phospho-
fructokinase
Aldolase
Dihydroxyacetone
phosphate (DHAP)
Figure 7.9-1b-s3 A closer look at glycolysis (part 1b, step 3)
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12. GLYCOLYSIS: Energy Payoff Phase
Figure 7.9-2
GLYCOLYSIS: Energy Payoff Phase
2 ATP 2
ATP
2 NADH
2 H2O
Glyceraldehyde
3-phosphate (G3P)
2 ADP
2 NA D+
+ 2 H+
2 ADP 2 2 2 2 2
Triose
phosphate
dehydrogenase
Phospho-
glycerokinase
Phospho-
glyceromutase
Enolase
Pyruvate
kinase
2 P i
1,3-Bisphospho-
glycerate
3-Phospho-
glycerate
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP)
Pyruvate
Figure A closer look at glycolysis (part 2: payoff phase)
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13. GLYCOLYSIS: Energy Payoff Phase
Figure 7.9-2a-s1
GLYCOLYSIS: Energy Payoff Phase
Glyceraldehyde
3-phosphate (G3P)
Isomerase
Aldolase
Dihydroxyacetone
phosphate (DHAP)
Figure 7.9-2a-s1 A closer look at glycolysis (part 2a, step 1)
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14. GLYCOLYSIS: Energy Payoff Phase
Figure 7.9-2a-s2
GLYCOLYSIS: Energy Payoff Phase
2 NADH
Glyceraldehyde
3-phosphate (G3P)
2 NAD+
+ 2 H+ 2
Triose
phosphate
dehydrogenase
2 P i
Isomerase
1,3-Bisphospho-
glycerate
Aldolase
Dihydroxyacetone
phosphate (DHAP)
Figure 7.9-2a-s2 A closer look at glycolysis (part 2a, step 2)
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15. GLYCOLYSIS: Energy Payoff Phase
Figure 7.9-2a-s3
GLYCOLYSIS: Energy Payoff Phase
2 ATP
2 NADH
Glyceraldehyde
3-phosphate (G3P)
2 NAD+
+ 2 H+
2 ADP 2 2
Triose
phosphate
dehydrogenase
Phospho-
glycerokinase
2 P i
Isomerase
1,3-Bisphospho-
glycerate
3-Phospho-
glycerate
Aldolase
Dihydroxyacetone
phosphate (DHAP)
Figure 7.9-2a-s3 A closer look at glycolysis (part 2a, step 3)
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16. GLYCOLYSIS: Energy Payoff Phase
Figure 7.9-2b-s1
GLYCOLYSIS: Energy Payoff Phase 2
Figure 7.9-2b-s1 A closer look at glycolysis (part 2b, step 1)
3-Phospho-
glycerate
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17. GLYCOLYSIS: Energy Payoff Phase
Figure 7.9-2b-s2
GLYCOLYSIS: Energy Payoff Phase
2 H2O 2 2 2
Phospho-
glyceromutase
Enolase
Figure 7.9-2b-s2 A closer look at glycolysis (part 2b, step 2)
3-Phospho-
glycerate
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP)
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18. GLYCOLYSIS: Energy Payoff Phase
Figure 7.9-2b-s3
GLYCOLYSIS: Energy Payoff Phase 2
ATP
2 H2O
2 ADP 2 2 2 2
Phospho-
glyceromutase
Enolase
Pyruvate
kinase
Figure 7.9-2b-s3 A closer look at glycolysis (part 2b, step 3)
3-Phospho-
glycerate
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP)
Pyruvate
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19. 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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20. CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE
Figure 7.UN07
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYL-
ATION
PYRUVATE
OXIDATION
GLYCOLYSIS
Figure 7.UN07 In-text figure, mini-map, pyruvate oxidation, p. 148
ATP
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21. 2 molecules per glucose) CYTOSOL
Figure 7.10
Pyruvate
(from glycolysis,
2 molecules per glucose)
CYTOSOL
PYRUVATE OXIDATION
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Figure 7.10 An overview of pyruvate oxidation and the citric acid cycle
CITRIC
ACID
CYCLE
2 CO2
FADH2
3 NAD+
3 NADH
FAD
+ 3 H+
ADP + P i
ATP
MITOCHONDRION
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22. 2 molecules per glucose) CYTOSOL
Figure
Pyruvate
(from glycolysis,
2 molecules per glucose)
CYTOSOL
PYRUVATE OXIDATION
CO2
NAD+
Figure An overview of pyruvate oxidation and the citric acid cycle (part 1: pyruvate oxidation)
CoA
NADH
+ H+
Acetyl CoA
CoA
MITOCHONDRION
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23. Acetyl CoA CoA CoA CITRIC ACID CYCLE 2 CO2 3 NAD+ FADH2 3 NADH FAD
Figure
Acetyl CoA
CoA
CoA
CITRIC
ACID
CYCLE
2 CO2
FADH2
3 NAD+
Figure An overview of pyruvate oxidation and the citric acid cycle (part 2: citric acid cycle)
3 NADH
FAD
+ 3 H+
ADP + P i
ATP
MITOCHONDRION
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24. 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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25. 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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26. CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE
Figure 7.UN08
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYL-
ATION
PYRUVATE
OXIDATION
GLYCOLYSIS
Figure 7.UN08 In-text figure, mini-map, citric acid cycle, p. 149
ATP
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27. CITRIC ACID CYCLE Figure 7.11-s1 Acetyl CoA Oxaloacetate Citrate
CoA-SH
H2O
Oxaloacetate
Citrate
Isocitrate
CITRIC
ACID
CYCLE
Figure 7.11-s1 A closer look at the citric acid cycle (step 1)
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28. CITRIC ACID CYCLE Figure 7.11-s2 Acetyl CoA Oxaloacetate Citrate
CoA-SH
H2O
Oxaloacetate
Citrate
Isocitrate
CITRIC
ACID
CYCLE
NAD+
NADH
+ H+
CO2
a-Ketoglutarate
Figure 7.11-s2 A closer look at the citric acid cycle (step 2)
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29. CITRIC ACID CYCLE Figure 7.11-s3 Acetyl CoA Oxaloacetate Citrate
CoA-SH
H2O
Oxaloacetate
Citrate
Isocitrate
CITRIC
ACID
CYCLE
NAD+
NADH
+ H+
CO2
CoA-SH
a-Ketoglutarate
Figure 7.11-s3 A closer look at the citric acid cycle (step 3)
CO2
NAD+
NADH
+ H+
Succinyl
CoA
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30. CITRIC ACID CYCLE Figure 7.11-s4 Acetyl CoA Oxaloacetate Citrate
CoA-SH
H2O
Oxaloacetate
Citrate
Isocitrate
CITRIC
ACID
CYCLE
NAD+
NADH
+ H+
CO2
CoA-SH
a-Ketoglutarate
Figure 7.11-s4 A closer look at the citric acid cycle (step 4)
CoA-SH
CO2
NAD+
NADH
Succinate P i
+ H+
GTP
GDP
Succinyl
CoA
ADP
ATP
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31. CITRIC ACID CYCLE Figure 7.11-s5 Acetyl CoA Oxaloacetate Citrate
CoA-SH
H2O
Oxaloacetate
Citrate
Isocitrate
CITRIC
ACID
CYCLE
NAD+
NADH
+ H+
CO2
Fumarate
CoA-SH
a-Ketoglutarate
Figure 7.11-s5 A closer look at the citric acid cycle (step 5)
CoA-SH
FADH2
CO2
NAD+
FAD
NADH
Succinate P i
+ H+
GTP
GDP
Succinyl
CoA
ADP
ATP
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32. CITRIC ACID CYCLE Figure 7.11-s6 Acetyl CoA Oxaloacetate Malate
CoA-SH
NADH
+ H+
H2O
NAD+
Oxaloacetate
Malate
Citrate
Isocitrate
CITRIC
ACID
CYCLE
NAD+
NADH
+ H+
H2O
CO2
Fumarate
CoA-SH
a-Ketoglutarate
Figure 7.11-s6 A closer look at the citric acid cycle (step 6)
CoA-SH
FADH2
CO2
NAD+
FAD
NADH
Succinate P i
+ H+
GTP
GDP
Succinyl
CoA
ADP
ATP
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33. Start: Acetyl CoA adds its two-carbon group to oxaloacetate, producing
Figure
Start: Acetyl CoA adds its
two-carbon group to
oxaloacetate, producing
citrate; this is a highly
exergonic reaction.
Acetyl CoA
CoA-SH
H2O
Figure A closer look at the citric acid cycle (part 1)
Oxaloacetate
Citrate
Isocitrate
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34. Isocitrate is oxidized; NAD+ is reduced.
Figure
Isocitrate
Redox reaction:
Isocitrate is oxidized;
NAD+ is reduced.
NAD+
NADH
+ H+
CO2
CO2 release
CoA-SH
a-Ketoglutarate
Figure A closer look at the citric acid cycle (part 2)
CO2
CO2 release
NAD+
Redox reaction:
NADH
After CO2 release, the resulting
four-carbon molecule is oxidized
(reducing NAD+), then made
reactive by addition of CoA.
+ H+
Succinyl
CoA
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35. Succinate is oxidized; FAD is reduced.
Figure
Fumarate
CoA-SH
FADH2
FAD
Redox reaction:
Succinate is oxidized;
FAD is reduced.
Succinate P i
GTP
GDP
Succinyl
Figure A closer look at the citric acid cycle (part 3)
CoA
ADP
ATP formation
ATP
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36. Redox reaction: Malate is oxidized; NAD+ is reduced. Oxaloacetate
Figure
Redox reaction:
Malate is oxidized;
NAD+ is reduced.
NADH
+ H+
NAD+
Oxaloacetate
Malate
Figure A closer look at the citric acid cycle (part 4)
H2O
Fumarate
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37. Figure 7.UN17 Test your understanding, question 13 (Coenzyme Q)
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