Cellular Respiration and Fermentation

Cellular Respiration and Fermentation
7 Cellular Respiration and Fermentation

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 3

Concept 7.1: Catabolic pathways yield energy by oxidizing organic fuels
Fermentation - partial degradation of sugars without O2 Aerobic respiration - degradation of sugars with O2 Anaerobic respiration - similar to aerobic respiration but consumes compounds other than O2 © 2014 Pearson Education, Inc. 4

C6H12O6  6 O2  6 CO2  6 H2O  Energy (ATP)
Cellular respiration includes both aerobic and anaerobic respiration but usually refers to aerobic 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) © 2014 Pearson Education, Inc. 5

The Principle of Redox redox reactions (oxidation-reduction) reactions that transfer electrons between reactants Oxidation - substance loses electrons Reduction - substance gains electrons © 2014 Pearson Education, Inc. 6

becomes oxidized (loses electron) becomes reduced (gains electron)
Figure 7.UN01 becomes oxidized (loses electron) becomes reduced (gains electron) Figure 7.UN01 In-text figure, NaCl redox reaction, p. 136 7

becomes oxidized becomes reduced
Figure 7.UN03 becomes oxidized becomes reduced Figure 7.UN03 In-text figure, cellular respiration redox reaction, p. 137 8

Stepwise Energy Harvest via NAD+ and the Electron Transport Chain
electron acceptor Coenzyme reduced form (NADH) passes electrons to electron transport chain to produce ATP © 2014 Pearson Education, Inc. 9

2 e− 2 H 2 e−  H NAD NADH H Dehydrogenase Reduction of NAD
Figure 7.4 2 e− 2 H 2 e−  H NAD NADH H Dehydrogenase Reduction of NAD  2[H] (from food)  H Oxidation of NADH Nicotinamide (reduced form) Nicotinamide (oxidized form) Figure 7.4 NAD+ as an electron shuttle 10

NAD Nicotinamide (oxidized form) Figure 7.4a
Figure 7.4a NAD+ as an electron shuttle (part 1: NAD+ structure) 11

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) 12

(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 13

The Stages of Cellular Respiration: A Preview
Glycolysis (breaks down glucose into 2 pyruvate) (color-coded teal throughout the chapter) Pyruvate oxidation and the citric acid cycle (color-coded salmon) Oxidative phosphorylation (color-coded violet) Animation: Cellular Respiration © 2014 Pearson Education, Inc. 14

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 15

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 16

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 17

Concept 7.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
Glycolysis breaks glucose into 2 pyruvate occurs in cytoplasm … 2 phases Energy investment phase Energy payoff phase occurs whether or not O2 is present © 2014 Pearson Education, Inc. 18

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 19

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 20

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) 21

Figure 7.9aa-1 Glycolysis: Energy Investment Phase Glucose Figure 7.9aa-1 A closer look at glycolysis (part 1a, step 1) 22

Figure 7.9aa-2 Glycolysis: Energy Investment Phase ATP Glucose 6-phosphate Glucose ADP Hexokinase 1 Figure 7.9aa-2 A closer look at glycolysis (part 1a, step 2) 23

Figure 7.9aa-3 Glycolysis: Energy Investment Phase ATP Glucose 6-phosphate Fructose 6-phosphate Glucose ADP Hexokinase Phosphogluco- isomerase 1 Figure 7.9aa-3 A closer look at glycolysis (part 1a, step 3) 2 24

Figure 7.9ab-1 Glycolysis: Energy Investment Phase Fructose 6-phosphate Figure 7.9ab-1 A closer look at glycolysis (part 1b, step 1) 25

Figure 7.9ab-2 Glycolysis: Energy Investment Phase Fructose 6-phosphate Fructose 1,6-bisphosphate ATP ADP Phospho- fructokinase Figure 7.9ab-2 A closer look at glycolysis (part 1b, step 2) 3 26

Figure 7.9ab-3 Glycolysis: Energy Investment Phase Glyceraldehyde 3-phosphate (G3P) Fructose 6-phosphate Fructose 1,6-bisphosphate ATP ADP Isomerase 5 Phospho- fructokinase Aldolase Dihydroxyacetone phosphate (DHAP) 4 Figure 7.9ab-3 A closer look at glycolysis (part 1b, step 3) 3 27

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) 28

Figure 7.9ba-1 Glycolysis: Energy Payoff Phase Glyceraldehyde 3-phosphate (G3P) Isomerase 5 Aldolase Dihydroxyacetone phosphate (DHAP) 4 Figure 7.9ba-1 A closer look at glycolysis (part 2a, step 1) 29

Figure 7.9ba-2 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 5 6 Aldolase Dihydroxyacetone phosphate (DHAP) 4 Figure 7.9ba-2 A closer look at glycolysis (part 2a, step 2) 30

Figure 7.9ba-3 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 7 3-Phospho- glycerate 5 6 Aldolase Dihydroxyacetone phosphate (DHAP) 4 Figure 7.9ba-3 A closer look at glycolysis (part 2a, step 3) 31

Figure 7.9bb-1 Glycolysis: Energy Payoff Phase 2 3-Phospho- glycerate Figure 7.9bb-1 A closer look at glycolysis (part 2b, step 1) 32

Figure 7.9bb-2 Glycolysis: Energy Payoff Phase 2 H2O 2 2 2 Phospho- glyceromutase Enolase 9 3-Phospho- glycerate 8 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) Figure 7.9bb-2 A closer look at glycolysis (part 2b, step 2) 33

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) 34

ENERGY-REQUIRING STEPS fructose–1,6–bisphosphate
Glycolysis ENERGY-REQUIRING STEPS OF GLYCOLYSIS glucose ATP 2 ATP invested ADP P glucose–6–phosphate P fructose–6–phosphate ATP ADP P P fructose–1,6–bisphosphate DHAP Fig. 8-4b, p.127

ENERGY-RELEASING STEPS 1,3–bisphosphoglycerate 1,3–bisphosphoglycerate
Glycolysis ENERGY-RELEASING STEPS OF GLYCOLYSIS P P PGAL PGAL NAD+ NAD+ NADH NADH Pi Pi P P P P 1,3–bisphosphoglycerate 1,3–bisphosphoglycerate substrate-level phsphorylation ADP ADP ATP ATP 2 ATP PRODUCED P P 3–phosphoglycerate 3–phosphoglycerate Fig. 8-4c, p.127

Glycolysis P P 2–phosphoglycerate 2–phosphoglycerate H2O H2O P P PEP
substrate-level phsphorylation ADP ADP ATP ATP 2 ATP produced pyruvate pyruvate Fig. 8-4d, p.127

Energy-Requiring Steps
2 ATP invested Energy-Requiring Steps of Glycolysis glucose ADP P ATP glucose-6-phosphate fructose-6-phosphate P ATP fructose1,6-bisphosphate P ADP PGAL P Figure 8-4(2) Page 127

1,3-bisphosphoglycerate 1,3-bisphosphoglycerate
PGAL PGAL NAD+ NAD+ Pi NADH Pi NADH P P P P 1,3-bisphosphoglycerate 1,3-bisphosphoglycerate ADP ADP ATP ATP P P 3-phosphoglycerate 3-phosphoglycerate P P 2-phosphoglycerate 2-phosphoglycerate H2O H2O P P PEP PEP ADP ADP ATP ATP pyruvate pyruvate Figure 8-4 Page 127

Concept 7.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules Pyruvate (3C) enters mitochondrion (when O2 is present) Then converted to acetyl coenzyme A (acetyl CoA)acetyl …2C), which enters citric acid (Krebs) cycle (the other C released as CO2) Completes breakdown to CO2 generating 1 ATP, 3 NADH, and 1 FADH2 per turn © 2014 Pearson Education, Inc. 40

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 41

Overview of Aerobic Respiration
CYTOPLASM glucose ATP 2 ATP 4 Glycolysis e- + H+ (2 ATP net) 2 NADH 2 pyruvate e- + H+ 2 CO2 Overview of Aerobic Respiration 2 NADH e- + H+ 8 NADH 4 CO2 KrebsCycle e- + H+ 2 ATP 2 FADH2 e- Electron Transfer Phosphorylation 32 ATP H+ water e- + oxygen Typical Energy Yield: 36 ATP Fig. 8-3, p. 135

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 43

2 molecules per glucose) CYTOSOL
Figure 7.10a Pyruvate (from glycolysis, 2 molecules per glucose) CYTOSOL CO2 NAD CoA Figure 7.10a An overview of pyruvate oxidation and the citric acid cycle (part 1: pyruvate oxidation) NADH  H Acetyl CoA MITOCHONDRION CoA 44

Citric acid cycle Acetyl CoA CoA CoA 2 CO2 FADH2 3 NAD 3 NADH FAD
Figure 7.10b Acetyl CoA CoA CoA Citric acid cycle 2 CO2 FADH2 3 NAD Figure 7.10b An overview of pyruvate oxidation and the citric acid cycle (part 2: citric acid cycle) 3 NADH FAD  3 H ADP  P i ATP 45

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 46

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) 47

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) 48

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 49

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 50

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 51

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 52

Start: Acetyl CoA adds its two-carbon group to oxaloacetate, producing
Figure 7.11a Start: Acetyl CoA adds its two-carbon group to oxaloacetate, producing citrate; this is a highly exergonic reaction. Acetyl CoA CoA-SH 1 H2O Oxaloacetate Figure 7.11a A closer look at the citric acid cycle (part 1) 2 Citrate Isocitrate 53

Isocitrate is oxidized; NAD is reduced.
Figure 7.11b Isocitrate Redox reaction: Isocitrate is oxidized; NAD is reduced. NAD NADH 3  H CO2 CO2 release CoA-SH -Ketoglutarate 4 Figure 7.11b A closer look at the citric acid cycle (part 2) CO2 release CO2 NAD Redox reaction: After CO2 release, the resulting four-carbon molecule is oxidized (reducing NAD), then made reactive by addition of CoA. NADH Succinyl CoA  H 54

Succinate is oxidized; FAD is reduced.
Figure 7.11c Fumarate 6 CoA-SH 5 FADH2 FAD Redox reaction: Succinate is oxidized; FAD is reduced. Succinate P i GTP GDP Succinyl CoA Figure 7.11c A closer look at the citric acid cycle (part 3) ADP ATP formation ATP 55

Redox reaction: Malate is oxidized; NAD is reduced. Oxaloacetate 8
Figure 7.11d Redox reaction: Malate is oxidized; NAD is reduced. NADH  H NAD 8 Oxaloacetate Malate 7 Figure 7.11d A closer look at the citric acid cycle (part 4) H2O Fumarate 56

next steps decompose citrate back to oxaloacetate, … a cycle
acetyl group of acetyl CoA joins cycle by combining with oxaloacetate, forming citrate next steps decompose citrate back to oxaloacetate, … a cycle each step catalyzed by a specific enzyme NADH and FADH2 relay electrons to electron transport chain which powers ATP synthesis via oxidative phosphorylation © 2014 Pearson Education, Inc. 57

each glucose makes up to 32 ATP
© 2014 Pearson Education, Inc. 58

The Pathway of Electron Transport
The electron transport chain is in the inner membrane (cristae) of the mitochondrion Carriers alternate between being reduced and oxidized (accept and donate electrons) Electrons drop in free energy as they go down the chain - finally passed to O2, forming H2O © 2014 Pearson Education, Inc. 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. 144 ATP ATP ATP 60

Free energy (G) relative to O2 (kcal/mol)
Figure 7.12 NADH 50 2 e− NAD FADH2 Multiprotein complexes 2 e− FAD 40 I FMN II Fe•S Fe•S Q III Cyt b 30 Fe•S Cyt c1 IV Free energy (G) relative to O2 (kcal/mol) Cyt c Cyt a Cyt a3 20 Figure 7.12 Free-energy change during electron transport 10 2 e− (originally from NADH or FADH2) 2 H  ½ O2 H2O 61

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 62

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 63

Electrons transferred from NADH or FADH2 to electron transport chain
The electron transport chain generates no ATP directly © 2014 Pearson Education, Inc. 64

Chemiosmosis: The Energy-Coupling Mechanism
Electron transfer in transport chain makes proteins pump H from the matrix to the intermembrane space The H gradient is referred to as a proton-motive force, emphasizing capacity to do work H moves back across the membrane through ATP synthase ATP synthase uses H flow to phosphorylate ATP This is an example of chemiosmosis, (use of H gradient energy to drive cellular work) © 2014 Pearson Education, Inc. 65

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 66

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 67

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 68

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 69

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 70

An Accounting of ATP Production by Cellular Respiration
cellular respiration, most energy flows: glucose  NADH  electron transport chain  proton-motive force  ATP About 34% of energy transferred to ATP, making about 32 ATP There are several reasons why the number of ATP molecules is not known exactly © 2014 Pearson Education, Inc. 71

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: 72

Electron shuttles span membrane 2 NADH or 2 FADH2 2 NADH Glycolysis 2
Figure 7.15a Electron shuttles span membrane 2 NADH or 2 FADH2 2 NADH Glycolysis 2 Pyruvate Glucose Figure 7.15a ATP yield per molecule of glucose at each stage of cellular respiration (part 1: glycolysis)  2 ATP 73

Pyruvate oxidation 2 Acetyl CoA Citric acid cycle
Figure 7.15b 2 NADH 6 NADH 2 FADH2 Pyruvate oxidation 2 Acetyl CoA Citric acid cycle Figure 7.15b ATP yield per molecule of glucose at each stage of cellular respiration (part 2: citric acid cycle)  2 ATP 74

2 NADH or 2 FADH2 2 NADH 6 NADH 2 FADH2 Oxidative phosphorylation:
Figure 7.15c 2 NADH or 2 FADH2 2 NADH 6 NADH 2 FADH2 Oxidative phosphorylation: electron transport and chemiosmosis Figure 7.15c ATP yield per molecule of glucose at each stage of cellular respiration (part 3: oxidative phosphorylation)  about 26 or 28 ATP 75

About Maximum per glucose: 30 or 32 ATP Figure 7.15d
Figure 7.15d ATP yield per molecule of glucose at each stage of cellular respiration (part 4: yield per glucose) 76

Anaerobic respiration uses final electron acceptor other than O2, for example, sulfate
© 2014 Pearson Education, Inc. 78

Types of Fermentation Fermentation - glycolysis plus reactions that regenerate NAD, (can be reused by glycolysis) 2 common types - alcohol fermentation and lactic acid fermentation © 2014 Pearson Education, Inc. 79

alcohol fermentation, pyruvate converted to ethanol
step 1 releases CO2 from pyruvate, step 2 reduces acetaldehyde to ethanol Alcohol fermentation by yeast used in brewing, winemaking, and baking Animation: Fermentation Overview © 2014 Pearson Education, Inc. 80

(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 81

(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 82

(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 83

Muscle cells use lactic acid fermentation when O2 is scarce
lactic acid fermentation, pyruvate reduced by NADH, forming lactate (no release of CO2) Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt Muscle cells use lactic acid fermentation when O2 is scarce © 2014 Pearson Education, Inc. 84

Comparing Fermentation with Anaerobic and Aerobic Respiration
All use glycolysis (net ATP  2) All use NAD different final electron acceptors Cellular respiration …32 ATP per glucose; fermentation produces …2 ATP per glucose © 2014 Pearson Education, Inc. 85

Obligate anaerobes …only anaerobic …and cannot survive in O2
facultative anaerobes…either fermentation or cellular respiration © 2014 Pearson Education, Inc. 86

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 87

The Evolutionary Significance of Glycolysis
Ancient prokaryotes - thought to have used glycolysis before oxygen in atmosphere little O2 available until about 2.7 billion years ago, so early prokaryotes likely used glycolysis too © 2014 Pearson Education, Inc. 88

The Versatility of Catabolism
Glycolysis accepts a wide range of carbohydrates Proteins digested to amino acids then amino groups removed before glycolysis or citric acid cycle © 2014 Pearson Education, Inc. 89

Fats digested to glycerol (used in glycolysis) and fatty acids
Fatty acids broken down to acetyl CoA gram of fat produces more than 2X more ATP than a gram of carbohydrate © 2014 Pearson Education, Inc. 90

Amino acids Fatty acids
Figure Proteins Carbohydrates Fats Amino acids Sugars Glycerol Fatty acids Figure The catabolism of various molecules from food (step 1) 91

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) 92

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 93

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 94

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 95

Figure 7.UN10b Figure 7.UN10b Skills exercise: making a bar graph and interpreting the data (part 2) 96

Inputs Glycolysis Glucose ATP  2 NADH
Figure 7.UN11 Inputs Outputs Glycolysis Glucose 2 Pyruvate  2 ATP  2 NADH Figure 7.UN11 Summary of key concepts: pyruvate 97

CO2 Inputs Outputs 2 Pyruvate 2 Acetyl CoA 2 ATP 8 NADH Citric acid
Figure 7.UN12 Inputs Outputs 2 Pyruvate 2 Acetyl CoA 2 ATP 8 NADH Citric acid cycle 2 Oxaloacetate CO2 6 2 FADH2 Figure 7.UN12 Summary of key concepts: citric acid cycle 98

(carrying electrons from food)
Figure 7.UN13a INTERMEMBRANE SPACE H H Protein complex of electron carriers H Cyt c IV Q III I Figure 7.UN13a Summary of key concepts: oxidative phosphorylation (part 1) II 2 H  ½O2 H2O FADH2 FAD NADH NAD MITOCHONDRIAL MATRIX (carrying electrons from food) 99

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 100

Overview of Aerobic Respiration
CYTOPLASM glucose ATP 2 ATP 4 Glycolysis e- + H+ (2 ATP net) 2 NADH 2 pyruvate e- + H+ 2 CO2 Overview of Aerobic Respiration 2 NADH e- + H+ 8 NADH 4 CO2 KrebsCycle e- + H+ 2 ATP 2 FADH2 e- Electron Transfer Phosphorylation 32 ATP H+ water e- + oxygen Typical Energy Yield: 36 ATP Fig. 8-3, p. 135

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