Carbon pathways

Jumars, P. A., D. H. Penry, J. A. Baross, M. J. Perry, and B. W. Frost. 1989. Closing the microbial loop Dissolved carbon pathway to heterotrophic bacteria from incomplete digestion and absorption in animals. Deep Sea Research 4 483-495. 

Werck-Reichhart, D., Jones, O.T.G., and Durst, F., Heme synthesis during cytochrome P-450 induction in higher plants. 5-Aminolevulinic acid synthesis through a five-carbon pathway in Helianthus tuberosus tuber tissues aged in the dark, Biochem. J., 249, 473 -80, 1988. 

The oxalate-carbonate pathway in soil carbon storage the role of fungi and oxalotrophic bacteria... 

A synthetic coupled cycle of calcium and carbon through the oxalate-carbonate pathway is shown in Fig. 12.8. Atmospheric CO2 is fixed by the plants through photosynthesis to produce biomass. Inside the plant, oxalate crystals form. In addition, fungal mycelium may also accumulate oxalate. Mainly in the form of calcium oxalate (COM or COD), this carbon pool is used by oxalotrophic bacteria as a carbon, energy and electron source. The transformation of oxalate can occur in the soil... 

Fig. 12.8. Simplified sketch showing main relationships inside the coupled calcium and carbon cycles of the oxalate-carbonate pathway in a hypothetical ecosystem. Plants and fungi are oxalate producers. Oxalotrophic bacteria (in the soil or animal guts) use oxalate as carbon, energy and electron sources, leading to CO2 and calcium carbonate production. Calcium carbonate can accumulate inside the soils. Because the carbon of the carbonate originates from organic carbon, its fossilization in the soil constitutes a carbon sink.

The initial two moles of organic carbon are both transformed into inorganic carbon. One mole is precipitated as a mineral, with carbon being trapped inside the calcium carbonate crystals, i.e. stored on a long-term time scale. The other mole can be released into the atmosphere and reused for phototrophy. Therefore, the oxalate-carbonate pathway constitutes a true carbon sink because one out of two moles of organic carbon is stored in a mineral state with a long residence time, whereas the other one returns to the atmospheric reservoir. 

R138 B. Bago, Y. Shachar-Hill and P. E. Pfeffer, Dissecting Carbon Pathways in Arbuscular Mycorrhizas with NMR Spectroscopy , p. 111... 

Calvin-Benson or three-carbon pathway catalyzed by ribulose biphospahate carboxilase oxygenase (Rubisco)... 

Hatch-Slack or four-carbon pathway catalyzed by phosphoenolpyruvate carboxylase. 

Figure /. The carbon pathways between interstellar and circumstellar regions and the forming solar system.

Reactions 6 (a and b) are intramolecular hydrogen eliminations which one would expect to be fast compared with the bimolecular hydrogen elimination Reactions 4 and 5 therefore the reactants of Reaction 5 can, in effect, be considered to yield the products of Reaction 6b. Now, if we let I approximate carbon, the essential components of the alternative benzene-to-carbon pathway are ... 

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Figiire 9.6. Carbon pathway screen for coal gasification option. 

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