Respiration and fermentation

Mohler, R.E., Dombek, K.M., Hoggard, J.C., Young, E.T., Synovec, R.E. (2006) Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry analysis of metabolites in fermenting and respiring yeast cells. Anal. Chem. 78 2700-2709. 

GA3P is subsequently converted, in a number of steps, into pyruvate (PYR), which is the branch-point between fermentation and respiration. Saccharomyces species are particularly well adapted to the anaerobic production of ethanol, via decarboxylation and reduction of PYR, to the near-exclusion of other metabolites. On account of this latter characteristic, as well as its high ethanol tolerance, Saccharomyces is the preferred organism to produce ethanol from hexoses. 

Oxireductases Dehydrogenases Oxidases Reductases Oxygenases Peroxidases Catalases Catalyze oxidation-reduction reactions. Important in fermentation and respiration pathways. 

In P. stipitis, fermentative and respirative metabolisms coexist to support cell growth and the conversion of sugar to ethanol [135]. The total respiration ca-... 

The essential steps depicting the branch point between fermentation and respiration are summarized in Fig. 7. Pyruvate dehydrogenase (Pdh) and Pdc compete for pyruvate. Either pyruvate can be oxidized via Pdh to form acetyl CoA, or it can be decarboxylated by Pdc to form acetaldehyde. The partitioning of pyruvate at this step is kinetically controlled. In S. cerevisiae, isolated mitochondria and purified Pdh exhibit much higher affinity (lower JC ,) for pyruvate... 

Fig. 7. Branch point between fermentation and respiration. At low pyruvate flux, the low of the Pdh complex for pyruvate results in oxidative decarboxylation to form acetyl CoA and NADH. The acetyl CoA can then can go into energy generation (via respiration) or fatty acid synthesis. At high glycolytic flux, pyruvate accumulates, and the higher of Pdc favors acetaldehyde formation and ethanol production. Accumulation of acetate can interfere with mitochondrial function. Pyk Pyruvate kinase Pdh pyruvate dehydrogenase Pdc pyruvate decarboxylase Aid (Dha) aldehyde dehydrogenase Adh alcohol dehydrogenase Acs acetyl CoA synthetase. (Taken from Postma et al. [169])...

It must be emphasized that the terms fermentation and respiration are not precisely defined in the literature. Here the term respiration includes only catabolic degradation of foods with 02 via the respiratory chain , but not the so-called substrate respiration . 

The first and second terms of Eq. 3 represent the diffusion through the particle and fluid reaction rate, respectively. The signal ( ) shows if the substance is being consumed (-) or formed (-f). The subscripts of the reaction rates Rj (h ) are related to the different subscripts of the factors (F,). Fj, F2, F3, F5, and Fe are parameters to be adjusted for the glycolytic and respiratory pathways (see Table 6). The synthetic composition X[5] (g/g dry mass basis) is responsible for the metabolic synthesis, fermentation, and respiration. 

The successes of the biochemist in elucidating the processes of fermentation and respiration and more recently the pathways of fat metabolism, are the direct results of viewing these processes not as individual physiological events, but as the resultant of a series of individual chemical reactions. In the same manner let us attempt to formulate an over-all picture of hormone action, in terms which do not hypothesize any particular mechanism or define the nature of the individual events. The physiological response (R) of a target cell to a hormone (h) may be con-... 

Depending on aerobic conditions, yeast can degrade sugars using two metabolic pathways alcoholic fermentation and respiration. These two processes begin in the same way, sharing the common trunk of glycolysis. 

Fermentation and Respiration Pasteur Effect and Crabtree Effect... 

A. Polysaccharides. B. Monosaccharides. C. Sugar Phosphates and Related Compounds. D. Unphosphorylated Intermediates and Products of Fermentation and Respiration. 

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