Another interesting feature of ethanol metabolism is that the
pathway of ethanol degradation (alcohol dehydrogenase followed
by acetaldehyde dehydrogenase) results in a net production of
reducing equivalents (2 NADH molecules per molecule of EtOH
Large amounts of EtOH increase the NADH/NAD+ ratio. This should
therefore stimulate respiration but as it happens acetaldehyde
inhibits the respiratory chain as well as acetaldehyde
dehydrogenase, its own converting enzyme. This leaves the liver
cells with an unmbalanced NADH/NAD+ ratio that potentially affects
many other pathways.
By the way, it is the production of NADH in the degradation of
EthOH that allows alcoholics to eat very little: they are getting
most of their energy from this pathway.
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