Oxidation reduction balance

The Acid-Base and Oxidation-Reduction Balances of the Earth... 

I apply these computational methods to various aspects of the Earth system, including the responses of ocean and atmosphere to the combustion of fossil fuels, the influence of biological activity on the variation of seawater composition between ocean basins, the oxidation-reduction balance of the deep sea, perturbations of the climate system and their effect on surface temperatures, carbon isotopes and the influence of fossil fuel combustion, the effect of evaporation on the composition of seawater, and diagenesis in carbonate sediments. These applications have not been fully developed as research studies rather, they are presented as potentially interesting applications of the computational methods. 

The details of the process and the oxidation-reduction balance can be pictured as in Eq. 17-25. Pyruvate is cleaved by the pyruvate formate-lyase reaction (Eq. 15-37) to acetyl-CoA and formic acid. Half of the acetyl-CoA is cleaved to acetate via acetyl-P with generation of ATP, while the other half is reduced in two steps to ethanol using the two molecules of NADH produced in the initial oxidation of triose phosphate (Eq. 17-25). The overall energy yield is three molecules of ATP per glucose. The "efficiency" is thus (3 x 34.5)... 

Other products can be produced in fermentative bacteria but the central feature of all these pathways is the strict maintenance of the oxidation-reduction balance within the fermentation system. This gives rise to another important tool in assessing fermentation pathways—a mass balance of the substrate and products. The amount of carbon, hydrogen and oxygen in the fermentation products (including cells) must correspond to the quantities in the substrate utilised. 

Equation 3 is a more specific formula for the metabolism of acetic acid and is developed from an oxidation-reduction balance using the appropriate yield constants as defined. 

The values for the organism yield constants are assumed to be somewhat higher than for acetic acid since they are expressed on a molar basis and more than one species may participate in the reaction. The yield constants for carbon dioxide and methane are developed from the oxidation-reduction balances. 

The ability of microbes to grow in an environment is influenced by its oxidation-reduction balance (redox potential), as they will require compatible terminal electron acceptors to permit their respiratory pathways to function. The redox potential even in fairly viscous emulsions may be quite high due to the appreciable solubility of oxygen in most fats and oils. 

Fig. 2.4. Oxidation-reduction balance of the thiol/ disulfide system...

The most significant role of 2,3-butanediol is in maintaining an oxidation-reduction balance with acetoin (or acetylmethyl carbinol) and diacetyl (Figure 2.7). This compound (2,3-butanediol) is formed following the reduction of acetoin, produced by the condensation of two ethanal molecules. 

Iron is very widespread in the earth s crust, representing a little over 5% of total mass. It is soluble in the form of ferrous and ferric chloride. Both forms occur in wine, maintaining an oxidation-reduction balance according to the electroactive redox system below ... 

Many fungicides and insecticides also contain one or more sulfur atoms. This is certainly true of dithiocarbamates, reduced to form thiocarbamic acids due to the oxidation-reduction balance. These compounds are reputedly as unstable as their oxygenated counterparts. Thiocarbamic acids are precursors of isothiocyauates, which constitute the active ingredients in fungicides (Figure 8.22). 

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