Phosphorylation electron transport

This process of creating ATP, known as electron transport phosphorylation, then, involves two half-cell reactions, one at the electron donation site and the other where the electrons are accepted from the transport chain. Taking aerobic sulfide oxidation as an example, the donating species H2S(aq) gives up electrons, two at a time, to a series of redox complexes. With the loss of each pair of electrons, the sulfide oxidizes first to S°, then thiosulfate, sulfite, and finally sulfate. 

Dopson M, Lindstrom EB, Hallberg KB. 2002. ATP generation dnring rednced inorganic snlfnr componnd oxidation by Acidithiobacillns caldns is exclnsively dne jto electron transport phosphorylation. ExtremophUes 6 123-9. 

There are two fermentative processes that at first appear to be quite similar to oxygen and nitrate-dependent respirations the reduction of C02 to methane and of sulfate to sulfide. However, on closer examination, it is clear that they bear little resemblance to the process of denitrification. In the first place, the reduction of C02 and of sulfate is carried out by strict anaerobes, whereas nitrate reduction is carried out by aerobes only if oxygen is unavailable. Equally important, nitrate respirers contain a true respiratory chain sulfate and C02 reducers do not. Furthermore, the energetics of these processes are very different. Whereas the free energy changes of 02 and nitrate reduction are about the same, the values are much lower for C02 and sulfate reduction. In fact, the values are so low that the formation of one ATP per H2 or NADH oxidized cannot be expected. Consequently, not all the reduction steps in methane and sulfide formation can be coupled to ATP synthesis. Only the reduction of one or two intermediates may yield ATP by electron transport phosphorylation, and the ATP gain is therefore small, as is typical of fermentative reactions. 

M. Baltscheffsky (1967c). Inorganic pyrophosphate as an energy donor in pholosynthetic and respiratory electron transport phosphorylation systems. Biochem. Biophys. Res. Commun., 28, 270-276. M. Baltscheffsky (1969). Reversed energy conversion reactions of bacterial photophospliorylation. 

Canonical denitrification is carried out by heterotrophic bacteria during which nitrate (or nitrite) serves as the terminal electron acceptor for organic matter oxidation and the nitrogen oxides are reduced mainly to nitrogen (some nitrous oxide may be formed). The characteristic feature of canonical denitrification is that the reduction of N-oxides is coupled to electron transport phosphorylation (Knowles, 1982, 1996 Koike and Hattori, 1975). The capacity for respiratory denitrification is widespread among bacteria and is distributed across various taxonomic subclasses, mainly within the Proteobacteria (Zumft, 1997). 

After it became clear that the reduction of CH3-S-C0M to CH4 consists of two reactions, one of these, the reduction of the heterodisulfide of CoM-S-H and H-S-HTP with H2 (Reaction 7 of Table 2), was considered to be the coupling site for ATP synthesis [14,71], Indeed, it was shown that everted vesicles of G61 also catalyzed the reduction of the heterodisulfide with H2 or with chemically reduced factor F420, F420H2, to H-S-CoM and H-S-HTP and that this reaction was coupled with the synthesis of ATP via the mechanism of electron transport phosphorylation [114-117] (Fig. 5) (i) the reduction of the heterodisulfide was associated with primary proton translocation at a ratio of up to 2H /CoM-S-S-HTP proton translocation was inhibited by protonophores rather than by DCCD (ii) reduction of the heterodisulfide was stimulated by protonophores and inhibited... 

Substrate level phosphorylation versus electron transport phosphorylation. 

Dissimilatory nitrate reduction to ammonium is an anaerobic pathway that is insensitive to NH4 and yields energy. The first step of the process is termed nitrate respiration because it is coupled to electron transport phosphorylation that generates ATP ... 

Dissimilatory Reduction of Nitrate to Ammonium by Microbial Cultures. We studied nitrate reduction to ammonia by an obligate anaerobe, Clostridium, which cannot gain energy from this reduction by electron transport phosphorylation, and by a number of Enterobacteri-aceae (known to be nitrate respirers) that can gain energy via the nitrate to nitrite step. All these organisms converted NOg" to as the... 

The third aerobic respiration stage takes place at the mitochondrial membrane, and is called electron transport phosphorylation. A hydrogen ion gradient is established and H+ flow drives formation of ATP from ADR Oxygen serves as the ultimate electron sink and produces water as a result. This stage yields 32 ATP molecules. 

Hackmann, T.J. and Firldns, J.L. (2015) Electron transport phosphorylation in rumen butyrivibrios unprecedented ATP yield for glucose fermentation to butyrate. Front Microbid., 6. 

D. B. Kell, On the Functional Proton Current Pathway of Electron Transport Phosphorylation—An Electrodic View, Biochim. Biophys. Acta 549, 55 (1979). 

Other biological systems exist, however, whose dynamic properties are much better known than those of cress root. Among these, properties of the membranes systems of electron transport phosphorylation have been studied from the point of view of bioenergies. This requires energy transport over relatively long distances, and other concepts that can all be supplied by various coherent excitations. Measurements to confirm this are now planned. 

A low concentration of substrate is one factor that might limit the rate of a reaction, and simple mass action control of respiration was an obvious possibility. Thus it was early suggested that respiration might be controlled at the stage of the transfer of electrons from DPNH to oxygen by the availability of ADP [6] or of P, [7], the substrates for electron transport phosphorylation. It could then be assumed that, when... 

The potential existence of futile cycles shows that mass action control would not be adequate. If such potential cycles actually functioned cyclically, the net reaction would be hydrolysis of ATP, and they would not be limited by mass action until the cell s ATP supply had been virtually abolished. More effective controls are evidently necessary. On the basis of current information, it seems unlikely that direct mass action effects play a primary role in the regulation of any metabolic processes. On the other hand, little is known about the regulation of electron transport phosphorylation, and the possibility of relatively simple mass action control of this process has not been ruled out. It would appear, however, that if such mass action controls exist, the limiting substrate is likely to be DPNH rather than ADP or P, since present evidence suggests that glycolysis and the citrate cycle, and thus the supply of DPNH, are tightly controlled. Thus even if mass action effects actually play a significant role in the control of electron transport phosphorylation, they are probably secondary to more flexible controls of other types. 

D.B.Kell, On the functional proton current pathway of electron transport phosphorylation, Biochim.Biophys.Acta 549 55 (1979). 

---