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Chapter 9 Cellular Respiration: Harvesting Chemical Energy

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[object Object],[object Object],Figure 9.1

[object Object],[object Object],Light energy ECOSYSTEM CO 2 + H 2 O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy Figure 9.2

Catabolic Pathways and Production of ATP ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

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Redox Reactions: Oxidation and Reduction ,[object Object],[object Object]

The Principle of Redox ,[object Object],[object Object]

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[object Object],Na + Cl Na + + Cl – becomes oxidized (loses electron) becomes reduced (gains electron)

[object Object],[object Object],[object Object],[object Object],[object Object],CH 4 H H H H C O O O O O C H H Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water + 2O 2 CO 2 + Energy + 2 H 2 O becomes oxidized becomes reduced Reactants Products Figure 9.3

Oxidation of Organic Fuel Molecules During Cellular Respiration ,[object Object],[object Object],[object Object],C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy becomes oxidized becomes reduced

Stepwise Energy Harvest via NAD + and the Electron Transport Chain ,[object Object],[object Object]

[object Object],[object Object],NAD + H O O O O – O O O – O O O P P CH 2 CH 2 HO OH H H HO OH HO H H N + C NH 2 H N H NH 2 N N Nicotinamide (oxidized form) NH 2 + 2[H] (from food) Dehydrogenase Reduction of NAD + Oxidation of NADH 2 e – + 2 H + 2 e – + H + NADH O H H N C + Nicotinamide (reduced form) N Figure 9.4

[object Object],[object Object],[object Object],(a) Uncontrolled reaction Free energy, G H 2 O Explosive release of heat and light energy Figure 9.5 A H 2 + 1 / 2 O 2

2 H 1 / 2 O 2 (from food via NADH) 2 H + + 2 e – 2 H + 2 e – H 2 O 1 / 2 O 2 Controlled release of energy for synthesis of ATP ATP ATP ATP Electron transport chain Free energy, G (b) Cellular respiration + Figure 9.5 B

The Stages of Cellular Respiration: A Preview ,[object Object],[object Object],[object Object],[object Object]

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[object Object],Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH 2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP ATP Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion Cytosol

[object Object],[object Object],Figure 9.7 Enzyme Enzyme ATP ADP Product Substrate P +

[object Object],[object Object],[object Object],Glycolysis Citric acid cycle Oxidative phosphorylation ATP ATP ATP 2 ATP 4 ATP used formed Glucose 2 ATP + 2 P 4 ADP + 4 P 2 NAD + + 4 e - + 4 H + 2 NADH + 2 H + 2 Pyruvate + 2 H 2 O Energy investment phase Energy payoff phase Glucose 2 Pyruvate + 2 H 2 O 4 ATP formed – 2 ATP used 2 ATP 2 NAD + + 4 e – + 4 H + 2 NADH + 2 H + Figure 9.8

Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate H H H H H OH OH HO HO CH 2 OH H H H H O H OH HO OH P CH 2 O P H O H HO HO H HO CH 2 OH P O CH 2 O CH 2 O P HO H HO H OH O P CH 2 C O CH 2 OH H C CHOH CH 2 O O P ATP ADP Hexokinase Glucose Glucose-6-phosphate Fructose-6-phosphate ATP ADP Phosphoglucoisomerase Phosphofructokinase Fructose- 1, 6-bisphosphate Aldolase Isomerase Glycolysis 1 2 3 4 5 CH 2 OH Oxidative phosphorylation Citric acid cycle Figure 9.9 A

2 NAD + NADH 2 + 2 H + Triose phosphate dehydrogenase 2 P i 2 P C CHOH O P O CH 2 O 2 O – 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase CH 2 O P 2 C CHOH 3-Phosphoglycerate Phosphoglyceromutase O – C C CH 2 OH H O P 2-Phosphoglycerate 2 H 2 O 2 O – Enolase C C O P O CH 2 Phosphoenolpyruvate 2 ADP 2 ATP Pyruvate kinase O – C C O O CH 3 2 6 8 7 9 10 Pyruvate O Figure 9.8 B

[object Object],[object Object],CYTOSOL MITOCHONDRION NADH + H + NAD + 2 3 1 CO 2 Coenzyme A Pyruvate Acetyle CoA S CoA C CH 3 O Transport protein O – O O C C CH 3 Figure 9.10

[object Object],ATP 2 CO 2 3 NAD + 3 NADH + 3 H + ADP + P i FAD FADH 2 Citric acid cycle CoA CoA Acetyle CoA NADH + 3 H + CoA CO 2 Pyruvate (from glycolysis, 2 molecules per glucose) ATP ATP ATP Glycolysis Citric acid cycle Oxidative phosphorylation Figure 9.11

Figure 9.12 Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA  -Ketoglutarate Isocitrate Citric acid cycle S CoA CoA SH NADH NADH FADH 2 FAD GTP GDP NAD + ADP P i NAD + CO 2 CO 2 CoA SH CoA SH CoA S H 2 O + H + + H + H 2 O C CH 3 O O C COO – CH 2 COO – COO – CH 2 HO C COO – CH 2 COO – COO – COO – CH 2 HC COO – HO CH COO – CH CH 2 COO – HO COO – CH HC COO – COO – CH 2 CH 2 COO – COO – CH 2 CH 2 C O COO – CH 2 CH 2 C O COO – 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation NAD + + H + ATP Citric acid cycle Figure 9.12

The Pathway of Electron Transport ,[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],H 2 O O 2 NADH FADH2 FMN Fe•S Fe•S Fe•S O FAD Cyt b Cyt c 1 Cyt c Cyt a Cyt a 3 2 H + + 1  2 I II III IV Multiprotein complexes 0 10 20 30 40 50 Free energy ( G ) relative to O 2 (kcl/mol) Figure 9.13

Chemiosmosis: The Energy-Coupling Mechanism ,[object Object],[object Object],INTERMEMBRANE SPACE H + H + H + H + H + H + H + H + P i + ADP ATP A rotor within the membrane spins clockwise when H + flows past it down the H + gradient. A stator anchored in the membrane holds the knob stationary. A rod (for “stalk”) extending into the knob also spins, activating catalytic sites in the knob. Three catalytic sites in the stationary knob join inorganic Phosphate to ADP to make ATP. MITOCHONDRIAL MATRIX Figure 9.14

[object Object],Oxidative phosphorylation. electron transport and chemiosmosis Glycolysis ATP ATP ATP Inner Mitochondrial membrane H + H + H + H + H + ATP P i Protein complex of electron carners Cyt c I II III IV (Carrying electrons from, food) NADH + FADH 2 NAD + FAD + 2 H + + 1 / 2 O 2 H 2 O ADP + Electron transport chain Electron transport and pumping of protons (H + ), which create an H + gradient across the membrane Chemiosmosis ATP synthesis powered by the flow Of H + back across the membrane ATP synthase Q Oxidative phosphorylation Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Figure 9.15

An Accounting of ATP Production by Cellular Respiration ,[object Object],[object Object]

[object Object],Electron shuttles span membrane CYTOSOL 2 NADH 2 FADH 2 2 NADH 6 NADH 2 FADH 2 2 NADH Glycolysis Glucose 2 Pyruvate 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis MITOCHONDRION by substrate-level phosphorylation by substrate-level phosphorylation by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol Maximum per glucose: About 36 or 38 ATP + 2 ATP + 2 ATP + about 32 or 34 ATP or Figure 9.16

Types of Fermentation ,[object Object],[object Object]

2 ADP + 2 P 1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Pyruvate 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 P 1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Lactate (b) Lactic acid fermentation H H OH CH 3 C O – O C C O CH 3 H C O CH 3 O – C O C O CH 3 O C O C OH H CH 3 CO 2 2 Figure 9.17

Fermentation and Cellular Respiration Compared ,[object Object],[object Object]

[object Object],Glucose CYTOSOL Pyruvate No O 2 present Fermentation O 2 present Cellular respiration Ethanol or lactate Acetyl CoA MITOCHONDRION Citric acid cycle Figure 9.18

The Evolutionary Significance of Glycolysis ,[object Object],[object Object],[object Object]

The Versatility of Catabolism ,[object Object],[object Object]

[object Object],Amino acids Sugars Glycerol Fatty acids Glycolysis Glucose Glyceraldehyde-3- P Pyruvate Acetyl CoA NH 3 Citric acid cycle Oxidative phosphorylation Fats Proteins Carbohydrates Figure 9.19

Biosynthesis (Anabolic Pathways) ,[object Object],[object Object],[object Object],[object Object]

Regulation of Cellular Respiration via Feedback Mechanisms ,[object Object],[object Object]

[object Object],Glucose Glycolysis Fructose-6-phosphate Phosphofructokinase Fructose-1,6-bisphosphate Inhibits Inhibits Pyruvate ATP Acetyl CoA Citric acid cycle Citrate Oxidative phosphorylation Stimulates AMP + – – Figure 9.20

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