Cellular Respiration and Fermentation 7 Cellular Respiration and Fermentation

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 © 2016 Pearson Education, Inc. 2

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 © 2016 Pearson Education, Inc.

Energy Investment Phase Figure 7.8 Energy Investment Phase Glucose 2 ATP used 2 ADP + 2 P 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+ © 2016 Pearson Education, Inc.

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 7.9-1 A closer look at glycolysis (part 1: investment phase) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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 7.9-2 A closer look at glycolysis (part 2: payoff phase) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc. 19

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

2 molecules per glucose) CYTOSOL Figure 7.10-1 Pyruvate (from glycolysis, 2 molecules per glucose) CYTOSOL PYRUVATE OXIDATION CO2 NAD+ Figure 7.10-1 An overview of pyruvate oxidation and the citric acid cycle (part 1: pyruvate oxidation) CoA NADH + H+ Acetyl CoA CoA MITOCHONDRION © 2016 Pearson Education, Inc.

Acetyl CoA CoA CoA CITRIC ACID CYCLE 2 CO2 3 NAD+ FADH2 3 NADH FAD Figure 7.10-2 Acetyl CoA CoA CoA CITRIC ACID CYCLE 2 CO2 FADH2 3 NAD+ Figure 7.10-2 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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc. 24

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 © 2016 Pearson Education, Inc. 25

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 © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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) © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

Start: Acetyl CoA adds its two-carbon group to oxaloacetate, producing Figure 7.11-1 Start: Acetyl CoA adds its two-carbon group to oxaloacetate, producing citrate; this is a highly exergonic reaction. Acetyl CoA CoA-SH H2O Figure 7.11-1 A closer look at the citric acid cycle (part 1) Oxaloacetate Citrate Isocitrate © 2016 Pearson Education, Inc.

Isocitrate is oxidized; NAD+ is reduced. Figure 7.11-2 Isocitrate Redox reaction: Isocitrate is oxidized; NAD+ is reduced. NAD+ NADH + H+ CO2 CO2 release CoA-SH a-Ketoglutarate Figure 7.11-2 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 © 2016 Pearson Education, Inc.

Succinate is oxidized; FAD is reduced. Figure 7.11-3 Fumarate CoA-SH FADH2 FAD Redox reaction: Succinate is oxidized; FAD is reduced. Succinate P i GTP GDP Succinyl Figure 7.11-3 A closer look at the citric acid cycle (part 3) CoA ADP ATP formation ATP © 2016 Pearson Education, Inc.

Redox reaction: Malate is oxidized; NAD+ is reduced. Oxaloacetate Figure 7.11-4 Redox reaction: Malate is oxidized; NAD+ is reduced. NADH + H+ NAD+ Oxaloacetate Malate Figure 7.11-4 A closer look at the citric acid cycle (part 4) H2O Fumarate © 2016 Pearson Education, Inc.

Figure 7.UN17 Test your understanding, question 13 (Coenzyme Q) © 2016 Pearson Education, Inc.