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* How does living cells utilize the chemical form of energy from organic molecules to generate ATP? * Light energy ECOSYSTEM Photosynthesis in chloroplasts CO2 H2O Cellular respiration in mitochondria ATP Heat energy Organic O2 molecules ATP powers most cellular work * * • • • • Exergonic !!! Fermentation: without O2 Aerobic respiration: use O2, yields ATP Anaerobic respiration: doesn’t use O2 * * becomes oxidized becomes reduced • • LEO goes GER Glucose = oxidized, oxygen = reduced * * NAD NADH Dehydrogenase Reduction of NAD (from food) Nicotinamide (oxidized form) Oxidation of NADH Nicotinamide (reduced form) * H2 1/2 O2 2H 1/ Explosive release of heat and light energy Free energy, G Free energy, G (from food via NADH) Controlled release of + 2H 2e energy for synthesis of ATP O2 ATP ATP ATP 2 e 2 1/ H+ H2O (a) Uncontrolled reaction 2 H2O (b) Cellular respiration 2 O2 * Electrons carried via NADH and FADH2 Electrons carried via NADH Glycolysis Glucose Pyruvate CYTOSOL Pyruvate oxidation Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis MITOCHONDRION ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation * Enzyme Enzyme ADP P Substrate ATP Product * Energy Investment Phase Glucose 2 ADP 2 P 2 ATP used Energy Payoff Phase 4 ADP 4 P 2 NAD+ 4 e 4 H+ 4 ATP formed 2 NADH 2 H+ 2 Pyruvate 2 H2O Net Glucose 4 ATP formed 2 ATP used 2 NAD+ 4 e 4 H+ 2 Pyruvate 2 H2O 2 ATP 2 NADH 2 H+ * MITOCHONDRION CYTOSOL CO2 Coenzyme A 3 1 2 Pyruvate Transport protein NAD NADH + H Acetyl CoA * Pyruvate CO2 NAD CoA NADH + H Acetyl CoA CoA Citric Acid Cycle (Krebs Cycle) CoA Citric acid cycle 2 CO2 3 NAD FADH2 3 NADH FAD + 3 H ADP + P i ATP * Acetyl CoA CoA-SH NADH + H H2O 1 NAD 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD Citric acid cycle 7 H2O Fumarate NADH 3 + H CO2 CoA-SH -Ketoglutarate 4 6 CoA-SH 5 FADH2 NAD FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H CO2 * Acetyl CoA CoA-SH H 2O 1 Oxaloacetate 2 Citrate Isocitrate * NADH 50 2 e NAD FADH2 Free energy (G) relative to O2 (kcal/mol) 2 e 40 FMN FeS FeS II Q III Cyt b 30 Multiprotein complexes FAD I FeS Cyt c1 IV Cyt c Cyt a 20 10 0 Cyt a3 2 e (originally from NADH or FADH2) 2 H + 1/2 O2 H2O * INTERMEMBRANE SPACE Chemiosmosis H Stator Rotor Internal rod Catalytic knob ADP + Pi ATP MITOCHONDRIAL MATRIX * H H H Protein complex of electron carriers Cyt c Q I IV III II FADH2 FAD NADH H 2 H + 1/2O2 ATP synthase H2O NAD ADP P i (carrying electrons from food) ATP H 1 Electron transport chain Oxidative phosphorylation 2 Chemiosmosis * Electron shuttles span membrane 2 NADH Glycolysis 2 Pyruvate Glucose MITOCHONDRION 2 NADH or 2 FADH2 2 NADH Pyruvate oxidation 2 Acetyl CoA 2 ATP Maximum per glucose: CYTOSOL 6 NADH 2 FADH2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis 2 ATP about 26 or 28 ATP About 30 or 32 ATP * 2 ADP 2 P Glucose i 2 ADP 2 P 2 ATP Glycolysis Glucose i 2 ATP Glycolysis 2 Pyruvate 2 NAD 2 Ethanol (a) Alcohol fermentation 2 NADH 2 H 2 NAD 2 CO2 2 Acetaldehyde 2 NADH 2 H 2 Pyruvate 2 Lactate (b) Lactic acid fermentation * Glucose CYTOSOL Glycolysis Pyruvate No O2 present: Fermentation O2 present: Aerobic cellular respiration MITOCHONDRION Ethanol, lactate, or other products Acetyl CoA Citric acid cycle * Proteins Carbohydrates Amino acids Sugars Glycolysis Glucose Glyceraldehyde 3- P NH3 Pyruvate Acetyl CoA Citric acid cycle Oxidative phosphorylation Fats Glycerol Fatty acids * Glucose AMP Glycolysis Fructose 6-phosphate Stimulates Phosphofructokinase Fructose 1,6-bisphosphate Inhibits Inhibits Pyruvate ATP Citrate Acetyl CoA Citric acid cycle Oxidative phosphorylation
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