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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Electrons from food 2e– Oxidation Energy-rich molecule Enzyme H Energy released for ATP synthesis Product Reduction High energy H +H+ H H H H 2e– H+ H NAD+ NAD+ H NAD NAD NAD+ 1. Enzymes that use NAD+ as a cofactor for oxidation reactions bind NAD+ and the substrate. 2. In an oxidation–reduction reaction, 2 electrons and a proton are transferred to NAD+, forming NADH. A second proton is donated to the solution. Low energy 3. NADH diffuses away and can then donate electrons to other molecules. 1/ O 2 2 2H+ H 2O 1 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reduction 2H Oxidation H+ Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. PEP Pyr uva te P Enzyme P P Enzyme P P – ADP – ATP P Ad Adenosine 3 eno sin e 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis Glucose NADH ATP ATP NADH Outer mitochondrial membrane Glycolysis Pyruvate Oxidation Intermembrane space Krebs Cycle Electron Transport Chain Chemiosmosis Pyruvate STEP A Glycolysis begins with the addition of energy. Two highenergy phosphates (P) from two molecules of ATP are added to the 6-carbon molecule glucose, producing a 6-carbon molecule with two phosphates. Pyruvate Oxidation NADH Priming Reactions 6-carbon glucose (Starting material) Mitochondrial matrix Acetyl-CoA ATP ATP ADP CO2 P ADP P Cleavage 6-carbon sugar diphosphate CO2 NADH Krebs Cycle e– NAD+ FAD O2 P ATP H 2O e– Electron e– Transport Chain ATP Inner mitochondrial membrane 3-carbon sugar phosphate P 3-carbon sugar phosphate Pi Pi NAD+ Oxidation and ATP Formation FADH2 Chemiosmosis ATP Synthase H+ NAD+ NADH NADH ADP ADP ATP ATP ADP ADP ATP ATP 3-carbon pyruvate 5 STEP B Then, the 6-carbon molecule with two phosphates is split in two, forming two 3-carbon sugar phosphates. STEPS C and D An additional Inorganic phosphate ( Pi ) is incorporated into each 3-carbon sugar phosphate. An oxidation reaction converts the two sugar phosphates into intermediates that can transfer a phosphate to ADP to form ATP. The oxidation reactions also yield NADH giving a net energy yield of 2 ATP and 2 NADH. 3-carbon pyruvate 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CH2OH Glycolysis: The Reactions Glucose Pyruvate Oxidation ADP Glucose 6-phosphate Fructose 6-phosphate 1,3-Bisphospho- Dihydroxyacetone Fructose glycerate Phosphate 1,6-bisphosphate 3 ATP Phosphofructokinase ADP Fructose 1,6-bisphosphate 2–3. Rearrangement, followed by a second ATP phosphorylation. 4 Aldolase 5 Isomerase 4–5. The 6-carbon molecule is split into two 3-carbon molecules—one G3P, another that is converted into G3P in another reaction. Dihydroxyacetone phosphate Pi NAD+ Pi NADH 6. Oxidation followed by phosphorylation produces two NADH molecules and two molecules of BPG, each with one high-energy phosphate bond. NADH Glyceraldehyde 3-phosphate dehydrogenase 1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate (BPG) (BPG) 7. Removal of high-energy phosphate by two ADP molecules produces two ATP molecules and leaves two 3PG molecules. Phosphoglycerate kinase 7 ATP 3-Phosphoglycerate (3PG) CH2 ATP CH2 O C O CH2OH O P 2-Phosphoglycerate (2PG) C Phosphoenolpyruvate Phosphoenolpyruvate (PEP) (PEP) C H C O2 O NADH NADH Acetaldehyde CHOH CH2 ETC in mitochondria NADH NAD+ Acetyl-CoA O P O CHOH NAD+ Lactate P O CH2 O– H C O C O Krebs Cycle P O– C O C O Ethanol P CH2 O– ADP 10 Pyruvate kinase Pyruvate P CO2 NAD+ O– Pyruvate ADP ATP O With oxygen H 2O O CH2 Phosphoenolpyruvate H 2O Enolase P CH2OH 9 H 2O O CHOH 2-Phosphoglycerate Phosphoglyceromutase 2-Phosphoglycerate (2PG) 10. Removal of high-energy phosphate by two ADP molecules produces two ATP molecules and two CH2 O ADP 3-Phosphoglycerate (3PG) CH2OH CH2 8 8–9. Removal of water yields two PEP molecules, each with a high-energy phosphate bond. Without oxygen Pyruvate P O O O P 3-Phosphoglycerate ADP P O O P Glyceraldehyde 3phosphate (G3P) 6 NAD+ CH2 Fructose 6-phosphate Phosphoglucose isomerase 2 Electron Transport Chain Chemiosmosis 1. Phosphorylation of glucose by ATP. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glucose 6-phosphate Hexokinase Krebs Cycle O 1 ATP Glyceraldehyde 3-phosphate ATP Glucose Glycolysis NADH ATP Pyruvate C O C O CH3 7 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis Glycolysis Pyruvate Oxidation Pyruvate Oxidation NADH NADH Krebs Cycle Krebs Cycle FADH2 CoA(Acetyl-CoA) 6-carbon molecule (citrate) NADH Electron Transport Chain Chemiosmosis Electron Transport Chain Chemiosmosis CoA 4-carbon molecule (oxaloacetate) ATP SEGMEN NAD + TA NADH NAD+ Pyruvate O– Pyruvate C ⎯ ⎯ O C ⎯ ⎯ O Acetyl Coenzyme A NAD+ NADH CoA Acetyl Coenzyme A S 4-carbon molecule CoA CH3 5-carbon molecule NAD+ T EN B NADH GM SE FAD 4-carbon molecule 4-carbon molecule SEGMENT C Two additional oxidations generate another NADH and an FADH2 and regenerate the original 4-C oxaloacetate. C ⎯ ⎯ O Krebs Cycle FADH2 SEGMENT B Oxidation reactions produce NADH. The loss of two CO2's leaves a new 4-C compound. 1 ATP is directly generated for each acetyl group fed in. CH 3 CO2 CO2 SEGMENT C Pyruvate Oxidation: The Reaction SEGMENT A Pyruvate from glycolysis is oxidized into an acetyl group that feeds into the citrate cycle. 2-C acetyl group combines with 4-C oxaloacetate to produce the 6-C compound citrate. ATP ADP + CO2 P 9 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis 1. Reaction 1: Condensation 2–3. Reactions 2 and 3: Isomerization Pyruvate Oxidation Glycolysis 4. Reaction 4: The first oxidation NADH 5. Reaction 5: The second oxidation Krebs Cycle FADH2 ATP 6. Reaction 6: Substrate-level phosphorylation Pyruvate Oxidation 7. Reaction 7: The third oxidation Electron T ransport Chain Chemiosmosis 8–9. Reactions 8 and 9: Regeneration of oxaloacetate and the fourth oxidation Krebs Cycle: The Reactions Krebs Cycle O═ C CH2 9 Malate dehydrogenase CH2 COO— ═ CH3— C— S 1 Citrate (6C) CH2 Citrate synthetase HO— C — COO— CH2 H++ COO— COO— Mitochondrial matrix 2 H 2O Aconitase 8 Fumarase 3 NADH dehydrogenase NADH + H+ — — — — — ═ — COO— CH 2H+ + 1/2O2 NAD+ CH2 HC 2 HO — CH FADH2 COO— 7 Succinate dehydrogenase Isocitrate dehydrogenase 4 Succinate (4C) ADP 6 GDP + Pi CO2 COO— CH2 CH2 C═ O ATP COO— Succinyl-CoA (4C) — — — — GTP S — CoA CH2 CoA-SH NAD+ FAD 22 e– C H+ H+ H+ H+ Intermembrane space CH2 α-Ketoglutarate dehydrogenase 5 — — — — — — — Succinyl-CoA synthetase COO— Inner mitochondrial membrane α-Ketoglutarate (5C) CoA-SH CH2 ADP + Pi H 2O Q NADH CH2 e– 22 e– NAD+ CO2 COO— ATP ATP synthase FADH2 HC — COO— COO— Cytochrome oxidase complex bc1 complex Isocitrate (6C) Fumarate (4C) COO— FAD ATP Electron Transport Chain Chemiosmosis COO— CoA-SH — — — — — — — — — — Malate (4C) COO— HO— CH NAD+ Oxaloacetate (4C) COO— — Acetyl-CoA O CoA NADH C —O a. The electron transport chain COO— b. Chemiosmosis NADH 11 12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis H+ Mitochondrial matrix NADH Glucose 2 ATP Pyruvate ATP Pyruvate Oxidation NADH ADP+Pi CO2 Acetyl-CoA Catalytic head NADH e- CO2 Krebs Cycle FADH2 32 ATP e- Stalk H+ 2 ATP H 2O 2H+ + 1 /2O2 e- Q C Rotor H+ H+ H+ Intermembrane space H+ H+ H+ H+ H+ H+ 13 14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis Glucose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glucose 2 ATP 2 ATP 6 ATP ADP Activates Fructose 6-phosphate Glycolysis Phosphofructokinase Pyruvate 2 NADH Inhibits Inhibits Fructose 1,6-bisphosphate Chemiosmosis Pyruvate oxidation 2 NADH 6 ATP 2 ATP 18 ATP Pyruvate Pyruvate Oxidation Pyruvate dehydrogenase ATP Krebs Cycle 6 NADH Acetyl-CoA Inhibits Chemiosmosis 2 FADH2 4 Krebs Cycle ATP Citrate NADH Total net ATP yield = 38 (36 in eukaryotes) Electron Transport Chain and Chemiosmosis 15 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alcohol Fermentation in Yeast Macromolecule degradation H H 2 ADP C OH Nucleic acids Proteins Polysaccharides Lipids and fats CH3 2 NAD+ 2 ATP 2 Ethanol Cell building blocks Nucleotides Amino acids Sugars Fatty acids 2 NADH O– H C O C O C CO2 CH3 Deamination O Glycolysis β-oxidation Oxidative respiration CH3 2 Acetaldehyde Pyruvate Lactic Acid Fermentation in Muscle Cells Acetyl-CoA O– 2 ADP H 2 ATP 2 O– NAD+ C O C OH Krebs Cycle CH3 2 Lactate 2 NADH C O C O Ultimate metabolic products NH3 H 2O CO2 CH3 17 18 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Urea NH3 19