Coupled respiration

Recently, a third piece of evidence was added by Chan and Freedman [161], who showed that an antibody towards subunit III specifically blocked proton translocation in cytochrome oxidase vesicles. Resting or coupled respiration was stimulated so that the respiratory control index fell by a factor of two. These findings exactly parallel those obtained by removal of subunit III [55,172]. 

Mitochondria can take part in antioxidant defence of the cell by maintaining low intracellular oxygen concentration. In fact, this may be regarded as removal of an excess of O2. Under resting conditions, this process seems to be carried out by partially uncoupled or non-coupled respiration [5]. 

Reduction of cytochrome br is also induced by coupled respiration with ascorbate and TMPD 17, cf. 8) or by an efflux of K+ from mitochondria by valinomycin 14). 

In a number of cases, the eflBciency of oxidative phosphorylation in the mitochondria of developing systems, as judged by the magnitude of the P 0 ratio, has been found to be less than that of mitochondria from fully differentiated tissues, and it has been suggested that such mitochondria may not yet have developed all of the fundamental machinery necessary for coupling respiration and phosphorylation [blowfly muscle (Lewis and Slater, 1954), rat muscle (Kiessling, 1962), honeybee flight muscle (Balboni, 1967), rat liver (Mintz et al., 1967), and rat brain (Milstein et al, 1968)]. 

NAD-linked phosphorulation coupled respiration Inhibited Holtzman et al, 1980... 

Glud RN, Ramsing NB, Revsbech NP. Photosynthesis and photosynthesis-coupled respiration in natural biofilms quantified with oxygen microsensors. J Phycol 1992 28 51-60. 

Upon comparing mitochondria from young and old rats, we did not detect any significant difference between them in their capacity to oxidise substrate, irrespeetive of the substrate used Indeed, in skeletal muscle mitochondria from old rats, there was never an inhibition of state 3 respiration (coupled respiration in which the synthesis and export of ATP is at the maximal rate), whether it was detected using FAD-linked substrate (i.e. succinate+rotenone) orNADH-linked substrate (glutamate + malate and pyruvate + malate) (Lombardi et cd., 2009 Kemer et al., 2001). In addition, we did not observe a difference (old vs. young) in the maximal eapaeity of mitochondria to oxidize lipid whether pahnitoyl-camitine or palmitoyl CoA+ eamitine was used as substrate. 

Other useful sensors rely on the coupling of microorganisms and electrochemical transducers. Changes in the respiration activity of the microorganism, induced by the target analyte, result in decreased surface concentration of electroactive metabolites (e.g., oxygen), which can be detected by the transducer. 

The rate of respiration of mitochondria can be controlled by the availability of ADP. This is because oxidation and phosphorylation are tightly coupled ie, oxidation cannot proceed via the respiratory chain without concomitant phosphorylation of ADP. Table 12-1 shows the five conditions controlling the rate of respiration in mitochondria. Most cells in the resting state are in state 4, and respiration is controlled by the availability of ADP. When work is performed, ATP is converted to ADP, allowing more respiration to occur, which in turn replenishes the store of ATP. Under certain conditions, the concentration of inorganic phosphate can also affect the rate of functioning of the respiratory chain. As respiration increases (as in exercise). 

Chlorate can serve as electron acceptor under anaerobic conditions (Thorell et al. 2003 Coates et al. 1999), and chlorate reductase has been found both in organisms such as Proteus mirabilis that can reduce chlorate but is unable to use to couple this to growth, and in true chlorate-respiring organisms. 

Myers CR, KH Nealson (1990) Respiration-linked proton translocation coupled to anaerobic reduction of manganese(IV) and iron (III) in Shewanella putrefaciens. J Bacteriol 172 6232-6238. 

Figure 18.2 Summary of respiratory energy flows. Foods ate converted into the reduced form of nicotinamide adenine dinucleotide (NADH), a strong reductant, which is the most reducing of the respiratory electron carriers (donors). Respiration can he based on a variety of terminal oxidants, such as O2, nitrate, or fumarate. Of those, O2 is the strongest, so that aerobic respiration extracts the largest amount of free energy from a given amount of food. In aerobic respiration, NADH is not oxidized directly by O2 rather, the reaction proceeds through intermediate electron carriers, such as the quinone/quinol couple and cytochrome c. The most efficient respiratory pathway is based on oxidation of ferrocytochrome c (Fe ) with O2 catalyzed by cytochrome c oxidase (CcO). Of the 550 mV difference between the standard potentials of c)Tochrome c and O2, CcO converts 450 mV into proton-motive force (see the text for further details).

In this chapter, a novel interpretation of the membrane transport process elucidated based on a voltammetric concept and method is presented, and the important role of charge transfer reactions at aqueous-membrane interfaces in the membrane transport is emphasized [10,17,18]. Then, three respiration mimetic charge (ion or electron) transfer reactions observed by the present authors at the interface between an aqueous solution and an organic solution in the absence of any enzymes or proteins are introduced, and selective ion transfer reactions coupled with the electron transfer reactions are discussed [19-23]. The reaction processes of the charge transfer reactions and the energetic relations... 

The reduction of O2 in W by hydroquinone derivatives (QH2) in O is a subject of interest, since the reaction might offer the fundamental information on the electron transport coupled with the proton transport at a biomembrane realized by the respiration [2,3,56]. 

In the present section, in order to elucidate the essential part of chemistry in the respiration, the redox reaction between O2 in W and QH2 in O was investigated by adopting QH2 the structure and chemical property of which is well known, and the proton transfer at the W/O interface accompanied by the redox reaction was elucidated. The transfer of various ions other than protons coupled with the redox reactions was also discussed. 

Biological growth is the result of the coupled synthesis-endogenous respiration reactions. The net result can be expressed as... 

The evolution of the isotope ratio at various depths is shown in Figure 8-11 for the first 200 years of the calculation. The shallowest depths depart little from the seawater value because they are diffusively coupled to open water. Respiration at somewhat greater depths drives the isotope ratio... 

In environments lacking a suitable external electron acceptor - such as dioxygen, sulfate, or ferric iron - respiration is not possible. Here, many organic compounds may be metabolized by fermenting microorganisms. Microbes of this class may create ATP by a direct coupling mechanism, using a process known as substrate level phosphorylation, SLP with an ion translocation mechanism like that employed by respirers, as already described or by a combination of SLP and ion translocation.1... 

Cytochrome c oxidase is an enzyme that couples the one-electron oxidation of cytochrome c to the four-electron reduction of 02 and is thus a crucial component of respiration. Cytochrome c contains the redox-active heme c, while cytochrome c oxidase contains a dinuclear Cua redox site in subunit II and three redox-active sites in subunit I heme a, heme a3, and Cur. It is believed that heme a is an electron-transfer site, while heme a3 and Cur function together at the 02 reduction site. 

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