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Glycolysis occurs in the cytoplasm and has two major phases:
Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate Glycolysis occurs in the cytoplasm and has two major phases: Energy investment phase Energy payoff phase Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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Energy investment phase
Fig. 9-8 Energy investment phase Glucose 2 ADP + 2 P 2 ATP used Energy payoff phase 4 ADP + 4 P 4 ATP formed 2 NAD e– + 4 H+ 2 NADH + 2 H+ Figure 9.8 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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Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate Fig. 9-9-1
Figure 9.9 A closer look at glycolysis Glucose-6-phosphate
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Glucose-6-phosphate 2 Phosphogluco- isomerase Fructose-6-phosphate
Fig Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate Glucose-6-phosphate 2 Phosphoglucoisomerase 2 Phosphogluco- isomerase Fructose-6-phosphate Figure 9.9 A closer look at glycolysis Fructose-6-phosphate
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Fructose- 1, 6-bisphosphate
Fig Glucose ATP 1 1 Hexokinase ADP Fructose-6-phosphate Glucose-6-phosphate 2 2 Phosphoglucoisomerase ATP 3 Phosphofructo- kinase Fructose-6-phosphate ATP 3 3 ADP Phosphofructokinase ADP Figure 9.9 A closer look at glycolysis Fructose- 1, 6-bisphosphate Fructose- 1, 6-bisphosphate
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Aldolase Isomerase Fructose- 1, 6-bisphosphate 4 5 Dihydroxyacetone
Fig Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate 2 Phosphoglucoisomerase Fructose- 1, 6-bisphosphate 4 Fructose-6-phosphate Aldolase ATP 3 Phosphofructokinase ADP Figure 9.9 A closer look at glycolysis 5 Isomerase Fructose- 1, 6-bisphosphate 4 Aldolase 5 Isomerase Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate
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Glyceraldehyde- 3-phosphate
Fig 2 NAD+ 6 Triose phosphate dehydrogenase 2 NADH 2 P i + 2 H+ 2 2 1, 3-Bisphosphoglycerate Glyceraldehyde- 3-phosphate 2 NAD+ 6 Triose phosphate dehydrogenase 2 P 2 NADH i + 2 H+ Figure 9.9 A closer look at glycolysis 2 1, 3-Bisphosphoglycerate
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2 2 ADP 2 ATP 2 3-Phosphoglycerate 1, 3-Bisphosphoglycerate 7
Fig 2 NAD+ 6 Triose phosphate dehydrogenase 2 NADH 2 P i + 2 H+ 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 1, 3-Bisphosphoglycerate 2 ADP 2 3-Phosphoglycerate 7 Phosphoglycero- kinase 2 ATP Figure 9.9 A closer look at glycolysis 2 3-Phosphoglycerate
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2 3-Phosphoglycerate 8 Phosphoglycero- mutase 2 2-Phosphoglycerate
Fig 2 NAD+ 6 Triose phosphate dehydrogenase 2 NADH 2 P i + 2 H+ 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 3-Phosphoglycerate 2 3-Phosphoglycerate 8 Phosphoglyceromutase 8 Phosphoglycero- mutase 2 2-Phosphoglycerate Figure 9.9 A closer look at glycolysis 2 2-Phosphoglycerate
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2 2-Phosphoglycerate Enolase 2 H2O 2 Phosphoenolpyruvate 9 Fig. 9-9-8
2 NAD+ 6 Triose phosphate dehydrogenase 2 NADH 2 P i + 2 H+ 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 2-Phosphoglycerate 2 3-Phosphoglycerate 8 Phosphoglyceromutase 9 Enolase 2 H2O 2 2-Phosphoglycerate 9 Enolase Figure 9.9 A closer look at glycolysis 2 H2O 2 Phosphoenolpyruvate 2 Phosphoenolpyruvate
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2 Phosphoenolpyruvate 2 ADP 10 Pyruvate kinase 2 ATP 2 Pyruvate
Fig 2 NAD+ 6 Triose phosphate dehydrogenase 2 NADH 2 P i + 2 H+ 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 Phosphoenolpyruvate 2 ADP 2 3-Phosphoglycerate 8 10 Phosphoglyceromutase Pyruvate kinase 2 ATP 2 2-Phosphoglycerate 9 Enolase 2 H2O Figure 9.9 A closer look at glycolysis 2 Phosphoenolpyruvate 2 ADP 10 Pyruvate kinase 2 ATP 2 Pyruvate 2 Pyruvate
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In the presence of O2, pyruvate enters the mitochondrion
Concept 9.3: The citric acid cycle completes the energy-yielding oxidation of organic molecules In the presence of O2, pyruvate enters the mitochondrion Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 3 Acetyl CoA Pyruvate
Fig. 9-10 CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 3 Acetyl CoA Figure 9.10 Conversion of pyruvate to acetyl CoA, the junction between glycolysis and the citric acid cycle Pyruvate Coenzyme A CO2 Transport protein
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The citric acid cycle, also called the Krebs cycle, takes place within the mitochondrial matrix
The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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Pyruvate CO2 NAD+ CoA NADH + H+ Acetyl CoA CoA CoA Citric acid cycle 2
Fig. 9-11 Pyruvate CO2 NAD+ CoA NADH + H+ Acetyl CoA CoA CoA Citric acid cycle 2 CO2 Figure 9.11 An overview of the citric acid cycle FADH2 3 NAD+ FAD 3 NADH + 3 H+ ADP + P i ATP
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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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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Figure 9.12 A closer look at the citric acid cycle
Acetyl CoA CoA—SH 1 Oxaloacetate Citrate Citric acid cycle Figure 9.12 A closer look at the citric acid cycle
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Figure 9.12 A closer look at the citric acid cycle
Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate Citric acid cycle Figure 9.12 A closer look at the citric acid cycle
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Figure 9.12 A closer look at the citric acid cycle
Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric acid cycle NADH 3 + H+ CO2 -Keto- glutarate Figure 9.12 A closer look at the citric acid cycle
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Citric acid cycle Succinyl CoA
Fig Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric acid cycle NADH 3 + H+ CO2 CoA—SH -Keto- glutarate Figure 9.12 A closer look at the citric acid cycle 4 CO2 NAD+ NADH Succinyl CoA + H+
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Citric acid cycle Succinyl CoA
Fig Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric acid cycle NADH 3 + H+ CO2 CoA—SH -Keto- glutarate Figure 9.12 A closer look at the citric acid cycle 4 CoA—SH 5 CO2 NAD+ Succinate P NADH i GTP GDP Succinyl CoA + H+ ADP ATP
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Citric acid cycle Succinyl CoA
Fig Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric acid cycle NADH 3 + H+ CO2 Fumarate CoA—SH -Keto- glutarate Figure 9.12 A closer look at the citric acid cycle 6 4 CoA—SH FADH2 5 CO2 NAD+ FAD Succinate P NADH i GTP GDP Succinyl CoA + H+ ADP ATP
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Citric acid cycle Succinyl CoA
Fig Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric acid cycle NADH 3 7 + H+ H2O CO2 Fumarate CoA—SH -Keto- glutarate Figure 9.12 A closer look at the citric acid cycle 6 4 CoA—SH FADH2 5 CO2 NAD+ FAD Succinate P P NADH i GTP GDP Succinyl CoA + H+ ADP ATP
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Citric acid cycle Succinyl CoA
Fig Acetyl CoA CoA—SH NADH +H+ 1 H2O NAD+ 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric acid cycle NADH 3 7 + H+ H2O CO2 Fumarate CoA—SH -Keto- glutarate Figure 9.12 A closer look at the citric acid cycle 4 6 CoA—SH FADH2 5 CO2 NAD+ FAD Succinate P NADH i GTP GDP Succinyl CoA + H+ ADP ATP
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