In article <2h110b$rmv at mserv1.dl.ac.uk> SCHLOSSER at ciit.org writes:
>In <9401120304.AA04594 at net.bio.net>
>mroussel at alchemy.chem.utoronto.ca (Marc Roussel) writes:
>>This is only possible if there is a reactant flux. A closed chemical
>>system (with or without enzyme) will always relax to a state of
>>thermodynamic equilibrium. Enzymes cannot alter the equilibrium state.
>>Yes, but on what time scale? A mixture of H2 and O2 is not at thermo.
>equilibrium, but sans spark the relaxation to equilibrium is not of
>practical significance.
That's true.
>I expect that the same would hold for the
>products of many enzymatic reactions.
If you have an ordinary enzyme (and not one that both catalyzes and
couples the reaction to some other in vivo reaction) that can't be true.
If the enzyme speeds up the reaction in one direction, it must do so by
lowering the activation energy but, because the laws of mechanics are
reversible, it must also lower the activation energy in the other
direction by an equal amount and thus hasten the approach to
the stationary state.
>For example I performed a series of
>experiments with yeast in which the the yeast was harvested and placed in
>an *anaerobic* medium containing glucose, but no nitrogen source. The
>glucose was completely consumed (to the limit of detection) being converted
>primarily to ethanol and glycerol. I didn't do the calculations, but this
>state is probably far from thermodynamic equilibrium.
I'm not so sure. I would like to do the calculations but I don't know
how the glycerol is generated. (It would be sufficient for me to know
the reactants and products of the reaction.) I take it that the ethanol
is generated by anaerobic fermentation.
Marc R. Roussel
mroussel at alchemy.chem.utoronto.ca
