Metabolism energetics

E.A. Newsholme, Substrate cycles their metabolic, energetic and thermic consequences in man, Biochem. Soc. Symp., 1978, 43, 183-205. 

The number of synthetic reactions known to involve coenzyme A is already large and is rapidly growing. Some of these are shown in Fig. 1. The implication of this coenzyme in the direct formation of high-energy addition products by pathways not involving the breakdown of ATP points to the quantitative importance of such mechanisms in the general picture of metabolic energetics. 

This type of correlation applies to almost any siibstrate involved in cellular energy metabolism and is supported by experimental data and energetic considerations. However, it is based on assumptions true at or near the steady-state equilibrium conditions and may not be valid... 

In order to develop a rational approach to improving rates of metabolite production, it is necessary to consider the fate of the nutrients that are required for its synthesis. However, overcoming the major flux control points within a metabolic pathway may not lead to metabolite overproduction if the energetic consequences of the alteration are unfavourable to the organism. 

Molecular hydrogen plays a major role on the oxidation-reduction processes involved in bacterial energetics, as well as in the degradation and conversion of biomass related with all major elemental cycles. Hydrogenase has a key role on this process and catalyzes the reversible oxidation of dihydrogen, important in bacterial anaerobic metabolism ... 

Janssen PH, B Schink (1995a) Metabolic pathways and energetics of the acetone-oxidizing sulfate-reducing bacterium Desulfobacterium cetonicum. Arch Microbiol 163 188-194. 

Marusak RA, Mears CF. 1995. Exploration of selected pathways for metabolic oxidative ring opening of benzene based on estimates of molecular energetics In Valentine JS, Foote CS, Greenberg A, Liebman JE, editors. Active Oxygen in Biochemistry. New York Chapman and Hall. p. 336. 

To get a deeper insight into the metabolic and energetic processes, knowledge of general principles of chemical energetics appears to be of help. 

With reference to the free energy as a characteristic of metabolism one may say that catabolic reactions proceed with a release of energy and anabolic ones, with a consumption of energy The anabolic reactions can proceed only as closely coupled to the catabolic reactions. High-energy, or macroergic, compounds act as energetic mediators between these two types of reactions. 

CMD = carbon metabolism determined, i.e., energetically independent. a This range results from differences in possible energy gains derived from the oxidation of formaldehyde. 

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