Respiration energy conversion with

Cytochrome c has a number of vital functions inside the cell. As part of the mitochondrial electron transport chain in respiration, it shuttles redox equivalents to cytochrome c oxidase (28), which can be considered as a kind of natural fuel cell for energy conversion. Mitochondrial dysfunction accompanied with changes in cytochrome c oxidase activity, however, seems to be intimately related to aging, neurodegeneration, and disease (29). Effects that can manipulate the fimctions of such redox enz5unes are therefore of great importance for many research fields. 

The overall statements for the energy conversions of biology have been known for more than a century. TTiey are embodied in the expressions for photosynthesis and respiration, as currently written and balanced for the formation and utilization of a carbohydrate such as glucose with six carbon (C) atoms and the equivalent of a molecule of water, H2O, for each carbon atom, consequently, the name carbohydrate. 

Electrochemistry is the study of mutual transformation of chemical and elec-frical energy. Specifically, it deals with chemical reactions driven by an electric current and with the electricity produced by chemical reactions. Examples of electrochemistry are electroplating, iron oxidation (rusting), solar-energy conversion, electrochemical conversions (fuel cells, bafferies), phofosynfhe-sis, and respiration. In this chapter, the principles of electrochemisfry are reviewed. First, let us briefly look info fhe history of electrochemisfry. 

Cellular respiration, which occurs in the presence of molecular oxygen, 02, and involves the conversion of pyruvate to carbon dioxide, C02, with the release of relatively large amounts of energy by way of intermediate chemical species... 

Solubilization, uptake, and precipitation of Ca and Si are directly (or at least energetically) linked to the photosynthetic and respiratory cycling of C, H, and O. Acids from nitrification and sulfur oxidation aid phosphorus mobilization photosynthesis or respiration is required for the uptake and conversion of phosphorous into high-energy phosphate. Sulfur is oxidized (with the concomitant reduction of nitrate) by Thiobacillus denitrificans, likewise, some extremely thermophilic methanogens can transfer hydrogen not only to CO2, but also to S. These are a few examples of interrelations involved in biogeochemical cycles. 

Oxidative phosphorylation is the culmination of a series of energy transformations that are called cellular respiration or simply respiration in their entirety. First, carbon fuels are oxidized in the citric acid cycle to yield electrons with high transfer potential. Then, this electron-motive force is converted into a proton-motive force and, finally, the proton-motive force is converted into phosphoryl transfer potential. The conversion of electron-motive force into proton-motive force is carried out by three electron-driven proton pumps—NADH-Q oxidoreductase, Q-cytochrome c oxidoreductase, and... 

In most aerobic cells the level of ATP exceeds that of ADP by 4- to 10-fold. Respiration depends on ADP as a substrate for phosphorylation. When ATP is consumed at high rates, accumulation of ADP stimulates respiration, with concomitant activation of ATP resynthesis. Conversely, in a relaxed and well-nourished cell, ATP accumulates at the expense of ADP, and the depletion of ADP limits the rate of both electron transport and its own phosphorylation to ATP. Thus, the energy-generating capacity of the cell is closely attuned to its energy demands. 

The membrane-active properties of Plnronic are rather nonspecific. Therefore, it is quite remarkable that both the ATP depletion and sensitization of MDR cells correlate with the expression of drug resistance proteins in these cells [33]. Figure 3 represents the correlation between the EC50 values, determined as the concentrations of the block copolymer that induced 50% depletion of ATP, and the levels of Pgp expression in various cells. As the expression of Pgp was increased, the ATP-depleting potency of the block copolymer was also elevated. This was related to the abnormally high energy consumption observed in MDR cells, which rendered them very responsive to respiratory inhibition by the block copolymer [27]. Conversely, the nonre-sistant cells were more hkely to adjust to the reduced respiration conditions... 

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