oxidative phosphorylation

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oxidative phosphorylation:

see phosphorylationphosphorylation,
chemical process in which a phosphate group is added to an organic molecule. In living cells phosphorylation is associated with respiration, which takes place in the cell's mitochondria, and photosynthesis, which takes place in the chloroplasts.
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Oxidative Phosphorylation

 

the synthesis in living cells of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and phosphoric acid at the expense of energy that derives from the oxidation of an organic substrate. As a result of oxidative phosphorylation, cells accumulate and subsequently utilize ATP—the most important high-energy compound known —to provide the energy for life processes. The principal substrates that are involved in oxidative phosphorylation are the organic acids that are formed in the tricarboxylic acid cycle.

Oxidative phosphorylation was first discovered in 1930 by the Soviet biochemist V. A. Engel’gardt. In 1939, V. A. Belitser and E. T. Tsybakova demonstrated that oxidative phosphorylation is associated with the transfer of electrons along the respiratory enzyme chain, which is located—as was later determined—in the inner mitochondrial membrane. Electrons enter the respiratory chain from reduced nicotinamide-adenine dinucleotide (NAD) or nicotinamide-adenine dinucleotide phosphate (NADP) and are successively transferred by coenzyme Q from compounds with a more negative oxidation-reduction potential to ones with a more positive potential.

The transfer of electrons along the chain terminates with the reduction of O2 by the complex enzyme cytochrome oxidase. Thus, substrate oxidation by oxygen is dependent on a series of oxidation-reduction reactions. After each reaction, the energy that accumulates in each molecule of oxidized substrate is released in small amounts, which ensures the maximum possible utilization of the energy; this maximum utilization occurs at energy conjugation points. The enzyme complex ATP-synthetase synthesizes ATP from ADP and phosphoric acid; it also controls the reverse process, the breakdown of ATP.

The ratio of P to O reflects the quantity of phosphate that is bonded during ADP phosphorylation relative to the amount of O2 that is absorbed. The transfer of two electrons through an energy conjugation point yields one molecule of ATP. The ratio of P to O is 3 for NAD oxidation and 2 for the oxidation of succinic acid.

S. A. OSTROUMOV

oxidative phosphorylation

[‚äk·sə‚dād·iv ‚fäs·fə·rə′lā·shən]
(biochemistry)
Conversion of inorganic phosphate to the energy-rich phosphate of adenosinetriphosphatase by reactions associated with the electron transfer system.
References in periodicals archive ?
Disrupting mitochondrial-nuclear coevolution affects OXPHOS complex I integrity and impacts human health," Genome Biology and Evolution, vol.
Usually, characteristic histopathology, metabolic studies, and enzymatic analysis of the OXPHOS respiratory chain may point the direction to a specific set of molecular studies.
However, on the other hand unlike nuclear DNA, mitochondrial DNA is not protected by histones and are physically associated with the inner mitochondrial membrane, where highly mutagenic oxygen radicals are generated as byproduct of OXPHOS in the respiratory chain (73) and leakage of these free radicals from the respiratory chain makes the mitochondria as a major intracellular source of ROS.
That is, even though the mitochondria of cancer cells are capable of making sufficient ATP to fuel/power their growth via OxPhos, such cells also make significant use of glycolysis to help make this ATP.
The results from muscle biopsies from 29 patients with deficiencies in PDHc and OXPHOS enzymes illustrate the rationale of our approach.
ATP levels were evaluated either in the absence or in the presence of glucose to sustain glycolysis and using oligomycin to inhibit OXPHOS activity.
But others, in order to survive, find a way to generate energy without the use of OxPhos.
OXPHOS assays were consistent with complex I deficiency.
A hallmark of cancer metabolism is the switch from oxidative phosphorylation (OXPHOS) to robust glycolysis, and deficits of OXPHOS have been associated with malignancy and cancer cell growth [4-6].
It was reported that OXPHOS deregulation stabilizes the transcription factor HIF1[alpha] promoting tumor growth [43].
Gnaiger, "High-resolution respirometry: OXPHOS protocols for human cells and permeabilized fibers from small biopsies of human muscle," Methods in Molecular Biology, vol.