Cellular Respiration: Harvesting Chemical Energy Cellular respiration – catabolic energy yielding pathway in which oxygen and organic fuels are consumed and ATP is produced SUMMARY: Organic + Oxygen Carbon + Water + Energy Compounds Dioxide C 6 H 12 O O 2 6 CO H 2 O + Energy C 6 H 12 O O 2 6 CO H 2 O oxidation reduction *By oxidizing glucose, energy is taken out of “storage” and made available for ATP synthesis

NAD + and NADP+ are electron shuttles

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

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 5) Conversion b/w the 2 3-carbon sugars 4) Cleavage into 2 3-carbon sugars

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

aerobic anaerobic The presence or absence of O 2 dictates the fate of pyruvate

The Krebs cycle: energy-yielding oxidation The junction b/w glycolysis and the Krebs cycle: Multienzyme complex: 1) Removal of CO 2 2) Electron transfer *pyruvate dehydrogenase 3) Addition of CoA

The Krebs cycle: energy-yielding oxidation 1) Addition of 2 Carbons Citrate synthase 2) Isomerization Aconitase 3) *Loss of CO 2 *electron transfer Isocitrate dehydrogenase 4) *Loss of CO 2 *electron transfer  -ketoglutarate dehydrogenase 5) substrate-level phosphorylation Succinyl CoA-synthetase 6) electron transfer Succinate dehydrogenase 7) Rearrangement of bonds Fumarase 8) electron transfer Malate dehydrogenase

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

*How does the mitochondrion couple electron transport and ATP synthesis? ATP synthase

Fermentation enables cell to produce ATP w/o O 2 aerobic anaerobic *Fermentation generates ATP by substrate-level phosphorylation