I'd like to raise a thought for discussion about free
radicals, a musing I heard from Robert Schimke one day. Do cells
need free radicals? Biochemical reactions are one source of free
radicals, where an intermediate or transition step often involves
an unpaired electron. If this reaction goes awry it releases
a free electron (to wreak havok and mahem). Might it not be possible
that biochemical reactions require free radicals to produce those
intermediate steps? If one thinks of a biochemical reaction as
having forward and reverse components, and the formation of an
intermediate step requiring an unpaired electron, then free radicals
as sources of unpaired electrons would favor the forward reaction
(to the intermediate step). Controlled free radicals may be a
requirement and the driving force behind biochemical reactions, without
which cellular metabolism would cease.
There are some other observations which support this idea.
All studies of cellular oxidative levels show at least some level
of free radicals; no cell is free from them. Expression
of free radical scavengers (superoxide dismutases, glutathione
reductases) can have antioxidant effects, but at high levels these
activities are toxic to cells, perhaps because they lower the
levels of free radicals too much.
Mike
