Oxidative phosphorylation during exercise

During the recovery period from exercise, ATP (newly produced by way of oxidative phosphorylation) is needed to replace the creatine phosphate reserves — a process that may be completed within a few minutes. Next, the lactic acid produced during glycolysis must be metabolized. In the muscle, lactic acid is converted into pyruvic acid, some of which is then used as a substrate in the oxidative phosphorylation pathway to produce ATP. The remainder of the pyruvic acid is converted into glucose in the liver that is then stored in the form of glycogen in the liver and skeletal muscles. These later metabolic processes require several hours for completion. 

During periods of recovery following exercise, creatine phosphate is regenerated at the expense of ATP synthesized from mitochondrial oxidative phosphorylation energy currency is paid into a reserve account, or reservoir, for the next period of sustained exercise. 

Mitochondrial oxidative ADP phosphorylation is the primary source of ATP in skeletal muscle during aerobic exercise. Thus, to maintain the tree-energy state of the cytoplasmic phosphoenergetic compounds ATP, ADP, and inorganic phosphate (PI), oxidative phosphorylation is modulated to match the rate of ATP utilization during exercise. The mitochondrial components of Wu et a/. s model are illustrated in Figure 7.13. Additional components include ATP hydrolysis, adenylate kinase,... 

Spectral Analysis. - A new method of analysis of ATP utilisation and resynthesis has been developed which simulates cellular ATP flux, mitochondrial oxidative phosphorylation and creatine kinase kinetics. The model was used to examine previously published P NMR data of changes in PCr and Pi in resting muscle, muscle exercising during ischaemia and muscle in aerobic recovery. The model allowed estimation of the maximal velocity of oxidative... 

Glycolysis produces NADH from NAD in Reaction 6 (G3P <=> 1,3BPG). In aerobic glycolysis, NADH is converted to NAD+ by the processes of electron transport and oxidative phosphorylation, which occur in the mitochondria. If oxygen is limiting (such as during heavy exercise), oxidative phosphorylation does not occur and NADH is not converted to NAD+. This could be disastrous if there were no other way to produce NAD... 

MRI of muscle as an means of assessing energy metabolism during exercise. Correlations were found between image intensity and intracellular pH, the time constant for PCr recovery and maximum oxidative phosphorylation. 

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