Anion respiration

The LundegSrdh hypothesis required that 4 monovalent anions and not more than 4 be absorbed per uptake of one O2 molecule in anion respiration and that all anions stimulate respiration to the same extent per anion charge absorbed. Experiment showed that neither condition was fulfilled. It also became clear that one of the ions whose uptake most enhanced respiration was the cation NH4 and that respiration was enhanced when ion uptake is restricted to cation uptake as occurs when a root is surrounded by a moist anion exchange resin. This hypothesis also preeludes an active uptake of ions occurring under anaerobic conditions following upon a period of active aerobic respiration it is a mechanism which would not provide for any storage of the ability to promote aetive ion uptake. In this it is contrary to a number of experimental observations. Further, only one carrier is postulated for all anions and it therefore fails to explain how there is no competition in uptake, for instance, between halide ions and sulphate ions, nor between sulphate and nitrate. It equally leaves unexplained competition between cations. 

Electron-transfer chains in plants differ in several striking aspects from their mammalian counterparts. Plant mitochondria are well known to contain alternative oxidase that couples oxidation of hydroquinones (e.g., ubiquinol) directly to reduction of oxygen. Semiquinones (anion-radicals) and superoxide ions are formed in such reactions. The alternative oxidase thus provides a bypass to the conventional cytochrome electron-transfer pathway and allows plants to respire in the presence of compounds such as cyanides and carbon monoxide. There are a number of studies on this problem (e.g., see Affourtit et al. 2000, references therein). 

The result of formate accumulation is metabolic acidosis. However, at later stages, the acidosis may also involve the accumulation of other anions such as lactate. This may be a result of inhibition of cytochrome oxidase and hence of mitochondrial respiration, tissue hypoxia due to reduced circulation of blood, or an increase in the NADH/NAD ratio. The acidosis that results from methanol poisoning will result in more formic acid being in the nonionized state and hence more readily able to enter the CNS. This will cause central depression and hypotension and increased lactate production. This situation is known as the "circulus hypoxicus."... 

It has been known for many years that the mitochondrion shows a respiration-linked transport of a number of ions. Of these, calcium has attracted the most attention since it depends on a specific transport system with high-affinity binding sites. The uptake of calcium usually also involves a permeant anion, but in the absence of this, protons are ejected as the electron transfer system operates. The result is either the accumulation of calcium salts in the mitochondrial matrix or an alkalinization of the interior of the mitochondrion. The transfer of calcium inwards stimulates oxygen utilization but provides an alternative to the oxidative phosphorylation of ADP618 ... 

There are several enzymes that convert 02 into 02. The superoxide ion is produced in many biological reactions and especially in respiration (see the review by Tselinski et al. 2001). Also, there are many indications that this anion radical is particularly toxic to cells and can ultimately have deleterious effects on the health and well-being of certain individuals see reviews by Lang Wagnerova (1992) andFaraggi Houee-Levin (1999). Moreover, the hydroxyl radical (which can be formed from 02 by the well-known Haber-Weiss reaction) also has very high toxicity (Sies 1986). 

Lehninger, A.L., 1974, Role of phosphate and other proton-donating anions in respiration-coupled transport of Ca2+ by mitochondria, Proc. Natl. Acad. Sci. USA 71, pp. 1520-1524 Lehninger, A.L., Carafoli, E., and Rossi, C. S., 1967, Energy-linked ion movements in mitochondrial systems, Adv. Enzymol. Relat. Areas. Mol. Biol. 29, pp. 259-320 Lemasters, J.J., Nieminen, A. L., Qian, T., Trost, L., Elmore, S. P., Nishimura, Y., Crowe, R. A., Cascio, W. E., Bradham, C. A., Brenner, D. A., and Herman, B., 1998, The mitochondrial permeability transition in cell death A common mechanism in necrosis, apoptosis and autophagy, Biochim. Biophys. Acta 1366, pp. 177-196... 

Let us analyze the ATP synthesis reaction (3.50), which, with respect to inorganic phosphate ion charge, requires one or two H+ ions for oxidation reaction. Figure 3.4 clearly illustrates that the H+-ATP-synthase responsible for oxidative phosphorylation consumes active H30+ particles (H+ ion) from both parts of the reaction system (matrix and cytoplasm). Specifying the work of H+-ATP-synthase, it should be noted that H+ ions delivered from the cytoplasm to the membrane and ADP and P substrates participate in phosphorylation reaction proceeding on the internal surface of the membrane. In this case, water molecules are one of the products of oxidative phosphorylation. It does not release to the volume, but dissociates to H + and OH ions immediately on the membrane. Then according to the chemiosmotic mechanism OH anion is desorbed to cytoplasm and H+ ion to the matrix, where its occurrence as the active particle is associated with water production at the final stage of the respiration process. 

In recent years newly invented detection devices have enabled scientists to investigate the minute quantities of materials that are involved in our metabolic processes. The super oxide anion (Op is one of the enemies of the cells of our bodies. It is generated as a by-product of respiration with oxygen and is also made by specially activated white blood cells. In normal healthy people the body has its own way of disposing of these ions using of an enzyme called super oxide... 

Superoxide dismutase, an enzyme that decomposes the un-needed enemy of the cell, superoxide anion (02 ), which is made as an unwanted by-product of cell respiration. 

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