Clicker Question #1 1. What compound directly provides energy for cellular work? A. DNA B. C6H12O6 C. glucose D. ATP E. fat 1

Energy Conversion Energy conversion Fuel rich in chemical energy Waste products poor in chemical energy Energy conversion Heat energy Gasoline  Oxygen Carbon dioxide  Water Combustion Kinetic energy of movement Energy conversion in a car Heat energy Cellular respiration Carbon dioxide  Water Food  Oxygen ATP Energy for cellular work Energy conversion in a cell 2

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 + Oxygen Carbon + Water + Energy Compounds Dioxide 3

Glucose loses electrons Oxygen gains electrons (and hydrogens) Cellular Respiration •By oxidizing glucose, energy is taken out of “storage” and made available for ATP synthesis Oxidation Glucose loses electrons (and hydrogens) C6H12O6  6 O2 6 CO2  6 H2O Glucose Oxygen Carbon dioxide Water Reduction Oxygen gains electrons (and hydrogens)

*Substrate-level phosphorylation Cellular Respiration *Substrate-level phosphorylation 3 metabolic stages: *glycolysis *Krebs cycle *electron transport chain and oxidative phosphorylation *Oxidative phosphorylation

2 2 ~34 ~38 ATP per glucose Mitochondrion Cytoplasm Cytoplasm Animal cell Plant cell Animal cell Plant cell Cytoplasm Cytoplasm Mitochondrion Mitochondrion High-energy electrons carried by NADH High-energy electrons carried by NADH High-energy electrons carried mainly by NADH High-energy electrons carried mainly by NADH Glycolysis Citric Acid Cycle Citric Acid Cycle 2 Pyruvic acid Glycolysis Electron Transport Glucose Electron Transport ~38 ATP per glucose 2 ATP 2 ATP ~34 ATP ATP ATP ATP Figure 6.6 6

Metabolic Disequilibrium *Multi-step open system

Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

Glycolysis: Energy Investment Phase 3) Addition of another phosphate group 1) Glucose is phosphorylated 4) Cleavage into 2 3-carbon sugars 2) G-6-P is rearranged 5) Conversion b/w the 2 3-carbon sugars

Glycolysis: Energy Payoff Phase 6) Two components: *electron transfer *Phosphate group addition Glycolysis: Energy Payoff Phase 9) Loss of water 7) ATP production 10) ATP production 8) Rearrangement of phosphate group

Fermentation enables cell to produce ATP w/o O2 aerobic anaerobic *Fermentation generates ATP by substrate-level phosphorylation

The presence or absence of O2 dictates the fate of pyruvate aerobic anaerobic

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 3) *Loss of CO2 *electron transfer Isocitrate dehydrogenase 7) Rearrangement of bonds Fumarase 4) *Loss of CO2 *electron transfer a-ketoglutarate dehydrogenase 6) electron transfer Succinate 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 Food Polysaccharides Fats Proteins Sugars Glycerol Fatty acids Amino acids Citric Acid Cycle Acetyl CoA Glycolysis Electron Transport ATP 18