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Clicker Question #1 1. What compound directly provides energy for cellular work? A. DNA B. C6H12O6 C. glucose D. ATP E. fat Energy Conversion Fuel rich in chemical energy Energy conversion Waste products poor in chemical energy Heat energy Gasoline Oxygen Combustion Kinetic energy of movement Energy conversion in a car Carbon dioxide Water Heat energy Food Oxygen Cellular respiration ATP Energy for cellular work Energy conversion in a cell Carbon dioxide Water Cellular Respiration Cellular respiration: A catabolic energy yielding pathway in which oxygen and organic fuels are consumed and ATP is produced • An aerobic process—it requires oxygen Summary equations: Organic Compounds + Oxygen Carbon + Water Dioxide + Energy Cellular Respiration •By oxidizing glucose, energy is taken out of “storage” and made available for ATP synthesis Oxidation Glucose loses electrons (and hydrogens) C6H12O6 Glucose 6 O2 Oxygen 6 CO2 Carbon dioxide 6 H2O Water Reduction Oxygen gains electrons (and hydrogens) Cellular Respiration *Substrate-level phosphorylation 3 metabolic stages: *glycolysis *Krebs cycle *electron transport chain and oxidative phosphorylation *Oxidative phosphorylation Mitochondrion Cytoplasm Cytoplasm Plant cell Animal cell Animal cell Plant cell Cytoplasm Cytoplasm High-energy High-energy electrons electrons carried carried NADH bybyNADH Glycolysis Glycolysis2 Glucose Pyruvic acid ATP 2 ATP Mitochondrion Mitochondrion High-energy High-energy electrons carried electrons carried mainly mainlyby by NADH NADH Citric Citric Electron Acid Electron Acid Transport Cycle Transport Cycle 2 ATP ATP ~34 ATP ATP ~38 ATP per Figure 6.6 Metabolic Disequilibrium *Multi-step open system Glycolysis harvests chemical energy by oxidizing glucose to pyruvate Glycolysis: Energy Investment Phase 1) Glucose is phosphorylated 2) G-6-P is rearranged 3) Addition of another phosphate group 4) Cleavage into 2 3-carbon sugars 5) Conversion b/w the 2 3-carbon sugars 6) Two components: *electron transfer *Phosphate group addition Glycolysis: Energy Payoff Phase 9) Loss of water 7) ATP production 8) Rearrangement of phosphate group 10) ATP production Fermentation enables cell to produce ATP w/o O2 anaerobic aerobic *Fermentation generates ATP by substrate-level phosphorylation The presence or absence of O2 dictates the fate of pyruvate anaerobic aerobic The Krebs cycle: energy-yielding oxidation The junction b/w glycolysis and the Krebs cycle: Multienzyme complex: 1) Removal of CO2 2) Electron transfer *pyruvate dehydrogenase 3) Addition of CoA The Krebs cycle: energy-yielding oxidation 8) electron transfer Malate dehydrogenase 1) Addition of 2 Carbons Citrate synthase 2) Isomerization Aconitase 7) Rearrangement of bonds Fumarase 6) electron transfer Succinate dehydrogenase 3) *Loss of CO2 *electron transfer Isocitrate dehydrogenase 4) *Loss of CO2 *electron transfer a-ketoglutarate dehydrogenase 5) substrate-level phosphorylation Succinyl CoA-synthetase Electron transport and ATP synthesis *Multi-step open system Generation and maintenance of an H+ gradient *Exergonic flow of e-, pumps H+ across the membrane *chemiosmosis high energy electrons ATP synthase *How does the mitochondrion couple electron transport and ATP synthesis? Versatility of Cellular Respiration – In addition to glucose, cellular respiration can “burn”: • Diverse types of carbohydrates • Fats • Proteins Polysaccharides Food Fats Sugars Glycerol Fatty acids Glycolysis Acetyl CoA ATP Proteins Amino acids Citric Acid Cycle Electron Transport
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