Respiratory chain phosphorylation

ATP formation coupled to electron flow in mitochondria is usually called oxidative phosphorylation. Because electron flow involves both reduction and oxidation, more appropriate names are respiratory phosphorylation and respiratory-chain phosphorylation, terminology that is also more consistent with photophosphorylation for ATP formation in photosynthesis. As with photophosphorylation, the mechanism of oxidative phosphorylation is not yet fully understood in molecular terms. Processes like phosphorylation accompanying electron flow are intimately connected with membrane structure, so they are much more difficult to study than are the biochemical reactions taking place in solution. A chemiosmotic coupling mechanism between electron flow and ATP formation in mitochondria is generally accepted, and we will discuss some of its characteristics next. 

Differentiation of the organelle for respiratory chain phosphorylation, requiring coordinated control of both nuclear and mitochondrial genes. This is independent of cell growth and division. 

Most forms of soluble arsenic are toxic to living organisms. Arsenate, a phosphate analog, uncouples respiratory chain phosphorylation due to the facile... 

The results of experiments to be described below appear to show that anoxia and cell poisons which inhibit respiratory chain phosphorylation stimulate uptake of glucose by muscle and that under suitable conditions respiration of fatty acids and ketone bodies can lead to inhibition of glucose uptake. Since fatty acids and ketone bodies are oxidized by mitochondria and since the effects of anoxia and of these cell poisons will be exerted principally on mitochondrial metabolism it seems reasonable to accept these findings as common evidence for a regulatory effect of mitochondrial metabolism on glucose uptake. It is recognized that this concept is provisional until such time as the mechanism of this regulation has been established. 

Effects of Anoxia and Inhibitors of Respiratory Chain Phosphorylation... 

The effects of thyroidectomy and of hyperthyroidism on uptake of glucose and on rates of membrane transport and phosphorylation of glucose in muscle have yet to be investigated. Since hyperthyroidism is associated with impaired efficiency of respiratory chain phosphorylation, it might be expected to accelerate membrane transport and phosphorylation of glucose (see Section IV, A, 1). 

Although this generalization was derived from a consideration of the differentiation of cells, it seems equally apphcable to mitochondria, for in these organelles are found the enzymes that operate in the tricarboxylic acid cycle, respiratory chain phosphorylation, transport of metabolites across mitochondrial membranes, amino acid and fatty acid metabolism, and synthesis of some mitochondrial constituents (Borst, 1969). 

Oxidative phosphorylation, respiratory chain phosphorylation formation of ATP coupled with the operation of the Respiratory chain (see). Energy available from the flow of electrons from substrate to oxygen via the respiratory chain drives the synthesis of ATP from ADP and inorganic phosphate. Oxidation of one molecule of reduced nicotinamide... 

Lehninoer, a. L. (1955). Oxidative phosphorylation. Harvey Lectures, 49,176-215, Slater, E. C. (1956). Respiratory chain phosphorylation. Proceedings of the S International Congress of Biochemistry, Brussels 1955. Academic Press, New York, 264-277. 

In the biochemical field, the central problem for future work is the function of vitamin K on the metabolic level. The hypothesis of the participation of vitamin Ki in the respiratory chain phosphorylation, put forward by Martius in 1953, is supported by new results. More work, however, is necessary to elucidate the exact mode of action of vitamin Ki or vitamin K2 compounds in this enzymatic system. Labeled K vitamins of high activity may be helpful for this purpose. 

Another important function of the kinases is the synthesis of ATP from ADP and energy-rich bound phosphate in substrate-linked phosphorylation (cf. Chapt. XV-7) and in respiratory-chain phosphorylation (Chapt. X-6). ATP hence represents a pool for energy-rich phosphates—and, in a sense, for chemical energy in general. 

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