Carbon dioxide bicarbonates

Carbonic anhydrase 4.2.1.1 Carbon dioxide Bicarbonate pH electrode... 

The pH-buffering of extracellular fluid depends in part on the carbon dioxide/ bicarbonate equilibrium so that the intake of sodium bicarbonate is followed by a brief alkalosis and an increased excretion of sodium carbonate in the urine. Depending on its carbonate concentration, the pH of the urine may rise to 8.07. Large doses (80—100 g/day) of sodium bicarbonate were needed if the pH of stomach contents was to be maintained at 4 or over in patients with duodenal ulcers8. Oxidation of organic anions in the body to carbon dioxide and water permits the use of sodium citrate, lactate or tartrate instead of sodium bicarbonate. In an analogous manner the ingestion of ammonium chloride induces a brief acidosis as a result of the metabolic conversion of ammonia to urea and lowers the pH of the urine. 

Yermilov V, Rubio J, Ohshima H (1995) Formation of 8-nitroguanine in DNA treated with peroxyni-trite in vitro and its rapid removal from DNA by depurination. FEBS Lett 376 207-210 Yermilov V, Yoshie Y, Rubio J, Oshima H (1996) Effects of carbon dioxide/bicarbonate on induction of DNA single-strand breaks and formation of 8-nitroguanine, 8-oxoguanine and base-propenal mediated by peroxynitrite. FEBS Lett 399 67-70... 

It is now possible to write equations for the activities of aqueous carbon dioxide, bicarbonate, and carbonate in terms of carbon dioxide partial pressure and hydrogen ion activity, by rearranging equations 1.6, 1.9, and 1.12. 

Thode H.G., Shima M., Rees C.E. and Krishnamurty K.V. (1965) Carbon-13 isotope effects in systems containing carbon dioxide, bicarbonate, carbonate, and metal ions. Can. J. Chem.. 43, 582-595. 

A. Denicola et al., Peroxynitrite reaction with carbon dioxide/ bicarbonate Kinetics and influence on peroxynitrite-mediated oxidations. Arch. Biochem. Biophys. 333,49-58 (1996)... 

As described in Chapter 2, the usual normal buffer system in culture media is the carbon dioxide-bicarbonate system, analogous to that in the blood. Modifications in the medium pH produce changes to the intracellular pH value, with modifications to enzyme activities. 

Mills G. A. and Urey H. C. (1940) The kinetics of isotopic exchange between carbon dioxide, bicarbonate ion, carbonate ion and water. J. Am. Chem. Soc. 62, 1019-1028. 

At this stage of development the model is restricted to a constant pH reactor and considers only two (pH and volatile acids concentration) of the five variables considered important for monitoring digester operation. This restriction of constant pH can be removed and the model extended to incorporate the interaction with bicarbonate alkalinity by considering the carbon dioxide-bicarbonate equilibrium as shown in Equations 16 and 17. 

In carbonic anhydrases, which catalyze the hydration/dehydration of carbon dioxide/bicarbonate ion ... 

Figure 1. (a) Cell arrangement for metal hydride hydrogen insertion reaction. Left side, acid reduction and hydrogen atom incorporation in palladium (Pd) foil membrane. Right side, electrostatic field for enhancement of carbon dioxide/bicarbonate adsorption on foil membrane, (b.) Blow-up of palladium/hydride foil showing hydrogen insertion into carbon dioxide. 

Hence, the Pd/PDH couple capable of directly reducing carbon dioxide/bicarbonate to methanol. 

A new method of reducing carbon dioxide/bicarbonate solutions to form methanol and other reduced products is presented. The method overcomes the traditional limitations of electrochemical reduction of carbon dioxide at a cathode in that both the surface potential and concentration of reducing species can be varied independently. 

Carbon atoms have varions oxidation states ranging from +4 to 4 (Table 5.1). The highest oxidized forms of carbon are carbon dioxide, bicarbonate, and carbonate, which is the end product of decomposition processes. Carbon fixation during photosynthesis produces reduced carbon (CH2O). Methane, another gaseons form of carbon, is the most reduced form and an end product of anaerobic decomposition process. 

Six of the 11 arsenite-oxidizing bacteria (all members of the a-Proteobacteria) were able to grow chemolithoautotrophically (i.e., aerobically in a minimal salts medium with arsenite as the electron donor and carbon dioxide-bicarbonate as the sole carbon source) (Table 1) (13). The time required for these bacteria to oxidize 5 mM arsenite varied from 3 days (for NT-25 and NT-26) to more than 5 days (for BEN-5). The arsenite was oxidized to an equivalent amount of arsenate and the pH of the medium decreased from 8.0 to 6.5. For all of the abovemen-tioned bacteria, no growth occurs in the absence of arsenite (i.e., only in an aerobic minimal salts medium containing carbon dioxide-bicarbonate). 

Aerobic growth in a minimal salts medium containing 5 mM arsenite as the electron donor and carbon dioxide-bicarbonate as the sole carbon source. 

---