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Chapter 7: Cellular Respiration pages 135-154
7.1 Catabolic Pathways yield energy by oxidizing organic fuels 7.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate 7.3 After pyruvate is oxidized, the citric acid cycle completes the energy yielding oxidation of organic molecules 7.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis 7.5 Fermentation and anaerobic respiration enable cells to produce ATP 7.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways C6H12O6 6 O2 6 CO2 6 H2O Energy (ATP heat)
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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 2
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Concept 7.1: Catabolic pathways yield energy by oxidizing organic fuels
The breakdown of organic molecules is _________ Fermentation: Aerobic respiration: Anaerobic respiration: Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration © 2014 Pearson Education, Inc. 3
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Figure 7.3 EXAMPLE OF A REDOX REACTION
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 4
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Bozeman Biology: Redox Reactions
Figure 7.UN03 becomes oxidized becomes reduced Figure 7.UN03 In-text figure, cellular respiration redox reaction, p. 137 Bozeman Biology: Redox Reactions 5
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The Importance of NAD+/NADH
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 6
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A Preview of Cellular Respiration
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 7
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Figure 7.7: Substrate Level Phosphorylation
Enzyme Enzyme ADP P Substrate ATP Figure 7.7 Substrate-level phosphorylation Product 8
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Concept 7.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
Glycolysis means: Glycolysis occurs in: Glycolysis occurs whether or not: © 2014 Pearson Education, Inc. 9
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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 10
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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) 11
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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) 12
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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 13
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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 © 2014 Pearson Education, Inc. 14
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Citric acid cycle Oxidative phosphorylation Pyruvate oxidation
Concept 7.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules Citric acid cycle Oxidative phosphorylation Pyruvate oxidation Glycolysis Figure 7.UN07 In-text figure, mini-map, pyruvate oxidation, p. 142 ATP ATP ATP 15
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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 16
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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 17
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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 18
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Oxidative phosphorylation: electron transport and chemiosmosis Citric
Concept 7.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis 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 19
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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 20
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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 21
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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 Bozeman Biology: ATP © 2014 Pearson Education, Inc. 22
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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: 23
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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… In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP 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 © 2014 Pearson Education, Inc. 24
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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 © 2014 Pearson Education, Inc. 25
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(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 26
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(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 27
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Comparing Fermentation with Anaerobic and Aerobic Respiration
All use ___________________ to oxidize glucose and harvest chemical energy of food In all three, ______ is the oxidizing agent that accepts electrons during glycolysis The processes have _________ final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and _____ in cellular respiration Cellular respiration produces _____ATP per glucose molecule; fermentation produces ____ ATP per glucose molecule © 2014 Pearson Education, Inc. 28
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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 29
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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 © 2014 Pearson Education, Inc. 30
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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 31
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Biosynthesis (Anabolic Pathways)
The body uses small molecules to build other substances Some of these small molecules come directly from food; others can be produced during glycolysis or the citric acid cycle Bozeman Biology Overview of Cellular Respiration: © 2014 Pearson Education, Inc. 32
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