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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation Energy-rich molecule Enzyme H Product Reduction H +H+ H H H H 2e– H+ H NAD+ NAD+ NAD H 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. 3. NADH diffuses away and can then donate electrons to other molecules. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Electrons from food 2e– Energy released for ATP synthesis High energy Low energy 1/ O 2 2 2H+ H2O 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reduction H+ 2H Oxidation 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. PEP P Enzyme Enzyme P P – ADP – ATP Adenosine 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Outer mitochondrial membrane Glycolysis Glucose NADH ATP Intermembrane space Pyruvate Pyruvate Oxidation NADH Mitochondrial matrix Acetyl-CoA CO2 CO2 NADH Krebs Cycle FADH2 e– NAD+ FAD O2 ATP H2O e– Electron e– Transport Chain ATP Inner mitochondrial membrane Chemiosmosis ATP Synthase H+ 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis ATP NADH Pyruvate Oxidation Krebs Cycle Electron Transport Chain Chemiosmosis 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. Priming Reactions 6-carbon glucose (Starting material) ATP ATP ADP P ADP P Cleavage 6-carbon sugar diphosphate P 3-carbon sugar phosphate P 3-carbon sugar phosphate Oxidation and ATP Formation Pi Pi NAD+ NAD+ NADH NADH ADP ADP ATP ATP ADP ADP ATP ATP 3-carbon pyruvate 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 Glucose Glycolysis: The Reactions NADH Glucose Pyruvate Oxidation Glucose 6-phosphate 2 Electron Transport Chain Chemiosmosis Phosphoglucose isomerase Fructose 6-phosphate 3 ATP Phosphofructokinase 1. Phosphorylation of glucose by ATP. ADP Fructose 1,6-bisphosphate 2–3. Rearrangement, followed by a second ATP phosphorylation. 7. Removal of high-energy phosphate by two ADP molecules produces two ATP molecules and leaves two 3PG molecules. Dihydroxyacetone phosphate Glyceraldehyde 3phosphate (G3P) 6 NAD+ Pi NAD+ Pi NADH NADH Glyceraldehyde 3-phosphate dehydrogenase 1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate (BPG) (BPG) 7 ADP ATP P ATP 3-Phosphoglycerate (3PG) CH2 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) 9 H2O H2O Enolase Phosphoenolpyruvate Phosphoenolpyruvate (PEP) (PEP) ADP 10 ADP ATP Pyruvate kinase ATP Pyruvate Pyruvate P O O O P CH2OH CH2 CH2 O P O P O CH2 O C O CH2OH O P C H C O CHOH CH2 O CHOH CH2 O P O– C O CHOH P O CH2 8 Phosphoglyceromutase P O O ADP Phosphoglycerate kinase 3-Phosphoglycerate (3PG) 8–9. Removal of water yields two PEP molecules, each with a high-energy phosphate bond. 10. Removal of high-energy phosphate by two ADP molecules produces two ATP molecules and two 5 2-Phosphoglycerate 6. Oxidation followed by phosphorylation produces two NADH molecules and two molecules of BPG, each with one high-energy phosphate bond. 4 Isomerase O– H C O C O P CH2OH Phosphoenolpyruvate 4–5. The 6-carbon molecule is split into two 3-carbon molecules—one G3P, another that is converted into G3P in another reaction. Aldolase CH2 Glyceraldehyde 3-phosphate Hexokinase ADP 1,3-Bisphospho- Dihydroxyacetone Fructose Fructose glycerate Phosphate 1,6-bisphosphate 6-phosphate Glucose 6-phosphate 1 ATP Krebs Cycle O 3-Phosphoglycerate ATP O– C O C O P CH2 O– Pyruvate Glycolysis C O C O CH3 7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Without oxygen Pyruvate H2O O2 With oxygen CO2 NAD+ NADH NADH Acetaldehyde ETC in mitochondria Acetyl-CoA NAD+ NADH Lactate NAD+ Krebs Cycle Ethanol 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis Pyruvate Oxidation NADH Krebs Cycle Electron Transport Chain Chemiosmosis Pyruvate Oxidation: The Reaction Pyruvate Pyruvate O– C O C O CH 3 CO2 NADH CoA Acetyl Coenzyme A Acetyl Coenzyme A NAD+ S CoA C O CH3 9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis Pyruvate Oxidation CoA(Acetyl-CoA) CoA NADH FADH2 Krebs Cycle 4-carbon molecule (oxaloacetate) ATP Electron Transport Chain Chemiosmosis 6-carbon molecule (citrate) NADH NAD + NADH NAD+ 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. 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. SEGMENT C Two additional oxidations generate another NADH and an FADH2 and regenerate the original 4-C oxaloacetate. CO2 4-carbon molecule Krebs Cycle 5-carbon molecule NAD+ FADH2 NADH FAD CO2 4-carbon molecule 4-carbon molecule ATP ADP + P 10 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 4. Reaction 4: The first oxidation 5. Reaction 5: The second oxidation NADH Krebs Cycle FADH2 ATP 6. Reaction 6: Substrate-level phosphorylation 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 Acetyl-CoA HO— CH O═C CH2 9 COO— ═ CH3— C— S Citrate (6C) COO— CoA-SH — — — — — — — Malate (4C) COO— — — — NADH NAD+ CoA — O Oxaloacetate (4C) COO— 1 CH2 Citrate synthetase HO— C — COO— Malate dehydrogenase CH2 CH2 COO— COO— 2 H2O Aconitase 3 8 Fumarase Isocitrate (6C) Fumarate (4C) COO— — — — — — ═ — COO— CH CH2 HC — COO— HC COO— HO — CH COO— FADH2 FAD 7 Succinate dehydrogenase Isocitrate dehydrogenase 4 Succinate (4C) NAD+ CO2 COO— — — — NADH CH2 -Ketoglutarate (5C) CoA-SH Succinyl-CoA synthetase GTP ADP 6 GDP + Pi CO2 COO— CH2 CH2 C═ O ATP COO— Succinyl-CoA (4C) S — CoA CH2 -Ketoglutarate dehydrogenase 5 CoA-SH — — — — COO— — — — — CH2 CH2 C —O NAD+ COO— NADH 11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis Pyruvate Oxidation Krebs Cycle ATP Electron Transport Chain Chemiosmosis H++ H ATP Mitochondrial matrix NADH dehydrogenase NADH + H+ Cytochrome oxidase complex bc1 complex 2H+ + 1/2O2 NAD+ ATP synthase ADP + Pi H2O FADH2 2 e– FAD 22 e– 22 e– Q Inner mitochondrial membrane C H+ H+ H+ H+ Intermembrane space a. The electron transport chain b. Chemiosmosis 12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H+ Mitochondrial matrix ATP ADP+Pi Catalytic head Stalk Rotor Intermembrane space H+ H+ H+ H+ H+ H+ 13 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis NADH Glucose 2 ATP Pyruvate Pyruvate Oxidation NADH CO2 Acetyl-CoA NADH CO2 Krebs Cycle e- H+ 32 ATP FADH2 2 ATP eH2O 2H+ + 1/ O 2 2 e- Q C H+ H+ H+ 14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glucose 2 ATP 2 ATP 6 ATP Glycolysis Pyruvate 2 NADH Chemiosmosis Pyruvate oxidation Krebs Cycle 2 6 NADH NADH 6 ATP 2 ATP 18 ATP Chemiosmosis 2 FADH2 4 ATP Total net ATP yield = 38 (36 in eukaryotes) 15 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis Glucose ADP Activates Fructose 6-phosphate Phosphofructokinase Inhibits Inhibits Fructose 1,6-bisphosphate Pyruvate Pyruvate Oxidation Pyruvate dehydrogenase ATP Acetyl-CoA Inhibits Citrate Krebs Cycle NADH Electron Transport Chain and Chemiosmosis 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alcohol Fermentation in Yeast H H C OH 2 ADP CH3 2 NAD+ 2 ATP 2 Ethanol 2 NADH O– C H O C O C CO2 CH3 O CH3 2 Acetaldehyde Lactic Acid Fermentation in Muscle Cells O– 2 ADP H 2 ATP 2 NAD+ O– C O C OH CH3 2 Lactate 2 NADH C O C O CH3 17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Macromolecule degradation Nucleic acids Proteins Polysaccharides Lipids and fats Cell building blocks Nucleotides Amino acids Sugars Fatty acids Glycolysis -oxidation Deamination Oxidative respiration Pyruvate Acetyl-CoA Krebs Cycle Ultimate metabolic products NH3 H2O CO2 18 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Urea NH3 19