Glycolysis Respiration Aerobic in the presence of oxygen Anaerobic in the absence of oxygen Respiration the oxygen dependent process of extracting energy from food glucose Summary of this process Sun s energy is now stored in the chemical bonds of glucose Animals acquire that energy by oxidizing glucose i e harvesting electrons from glucose The exergonic downhill breakdown of glucose drives the endergonic uphill reaction that makes ATP Three step process 1 Glycolysis occurs in cytosol anaerobic 2 Krebs cycle occurs in mitochondrion aerobic 3 Electron Transport occurs in mitochondrion Glycolysis is an anaerobic process it is found in all organisms both prokaryotes and eukaryotes Respiration Krebs and Electron Transport is an aerobic process Glycolysis sugar splitting 1 Note the initial investment of energy the first step uses ATP 2 6 carbon glucose molecule is split into two 3 carbon sugars 3 3 carbon sugar is oxidized NAD is reduced to NADH This happens twice so result is two NADH molecules 4 Sugars lose phosphate groups four ATP are formed 5 End product is 2 pyruvic acid Final balance sheet for glycolysis 2 ATP 4 minus the initial 2 2 NADH stored energy 2 molecules of pyruvic acid Three fates of pyruvic acid 1 Fermentation by yeast to ethanol 2 Production of lactic acid 3 Enters mitochondrion and on to Krebs cycle Respiration Krebs cycle and electron transport is an aerobic process Krebs Cycle Krebs cycle takes place in mitochondrial matrix Krebs cycle is exergonic downhill reaction that harvests and stores energy Calvin cycle is endergonic uphill Main purpose of the Krebs cycle is to generate more energy carrying NADH and FADH2 molecules Note carbon dioxide has been returned to atmosphere Final balance sheet for the Krebs Cycle 2 x 3 6 NADH 2 x 1 2 FADH2 2 x 1 2 ATP 2 x 2 4 CO2 90 of energy of glucose is now stored in NADH and FADH2 Electron Transport Occurs in mitochondria on the inside of the inner membrane Release of energy from NADH and FADH2 through electron transport chain drives a phosphate onto ADP to make ATP ADP P ATP The way it works Hydrogen ions are pumped into inter membrane space potential energy Ions stream back into matrix through ATP synthase ATP yield from Electron Transport 34 ATP Total ATP from one molecule of glucose 38 ATP Oxygen is final electron acceptor after electron transport THIS is why we breathe Trained endurance Athletes Have more and bigger mitochondria more enzyme process more oxygen higher aerobic capacity higher anaerobic threshold increased endurance speed
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