Alcohol energy yield

When glycolysis occurs under anaerobic conditions, it is followed by fermentation reactions, such as the lactate and alcohol fermentations. These reactions reduce pyruvate—or a molecule produced from pyruvate—and simultaneously oxidize the NADH produced in glycolysis. As a result, the net energy yield from glycolysis under anaerobic conditions is only two ATP. No further ATP energy is harvested from the oxidation of the NADH. It is simply reoxidized in the fermentation reactions. 

Fermentation is defined as an energy-yielding metabolic pathway that involves no net change in oxidation state. Anaerobic glycolysis is a type of fermentation. The lactic acid fermentation (conversion of glucose to lactate) is important in the manufacture of cheese. Another important fermentation involves cleavage of pyruvate to acetaldehyde and C02, with the acetaldehyde then reduced to ethanol by alcohol dehydrogenase in the reaction that follows ... 

B) The energy yield from alcohol utilization is dramatically reduced. 

With increasing alcohol concentration non-bulk electrostatic contributions become relevant. Because these non-bulk electrostatic contributions depend on the concentration of the cosolvent as well on the size of the alkyl-group, one can conclude that there is a relation to the smaller free energy necessary for exposing hydrophobic surfaces to the medium. It yields ... 

Reactions involve several enzymes, which have to follow in sequence for lactic acid and alcohol fermentation. This is known as the glucose catabolism pathway, with emphasis on energetic and energy carrier molecules such as ATP, ADP, NAD+ and NADH. In this pathway the six-carbon substrate yields two three-carbon intermediates, each of which passes through a sequence of reactions to the stable end product of pyruvic acid. 

The observation that in the case of PCSO there is no formation of propanol while allyl alcohol is formed from ACSO agrees with the resonance stabilization of the allyl radical60 and hence weaker bond for S-allyl than for S-propyl. The yield of allyl alcohol from irradiation of ACSO is considerably greater than that from S-allyl-L-cysteine, probably due to energy delocalization by the four p electrons of the S atom. 

In order to go further into the experimental check we constructed Arrhenius plots of the fluorescence quantum yield of BMPC in a few solvents (methanol, ethanol, propanol, hexanol and methylene chloride), all of which showed good linearity. The activation energies and A/kp ratios, calculated from the slopes and intercepts of those plots, are collected in Table 1. The smooth increase of both parameters in the alcohol series is mainly associated with the increase of solvent viscosity. On the other hand, decrease of the solvent dielectric constant from 32.7 (methanol) to 8.9 (dichloromethane) causes a small but significant increase of the activation energy also, this increase is probably somewhat compensated by the decrease of the viscous-flow... 

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