Control of Energy Flux in Biological Systems
Cells, in order to survive and grow, must maintain precise dynamic balance between the pathways which utilize ATP (biosynthetic pathways, ion transport, etc.) and those which produce ATP (glycolysis, mitochondrial oxidative phosphorylation). In higher organisms most of the ATP is supplied by mitochondrial oxidative phosphorylation. Complete aerobic combustion of glucose to carbon dioxide and water yields approximately 17 times as much useful energy in the form of ATP as can be obtained from the same glucose by anaerobic glycolysis alone. The overwhelming importance of mitochondrial oxidative phosphorylation in man becomes apparent when one realizes that a 69 kg man walking at 4 km/h in loose snow and carrying a 20 kg load is utilizing approximately 0.5 kg of ATP/minute! During a normal working day the ATP utilization of the same man may range from approximately 25 g ATP/min to values in excess of 0.6 kg ATP/min. This high metabolic flux and large dynamic range of control assures mitochondrial oxidative phosphorylation of a dominant role in cellular homeostasis.
KeywordsHydrolysis Glycerol Chrome Lactate Respiration
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