On Sat, 27 Dec 2003 01:40:06 +0000 (UTC), Andrew Glasgow
 wrote:

>With all the scientific interest, and not-so-scientific hype regarding 
>antioxidants I've been reading lately, I gave some thought to it.  It 
>seems to me that given their function -- preventing damage to DNA and 
>thereby reducing the chances of cancer -- all multicellular and probably 
>most unicellular organisms must have a suite of antioxidant chemicals 
>evolved to the optimal balance between longer life and cellular 
>efficiency.
>
>It occurs to me that there is an explanation why all the antioxidants 
>we're hearing so much about occur in plants rather than animals.  
>Animals must have antioxidants as well but most of those in animals are 
>similar to the ones our body produces so introducing them into our 
>system causes our body to produce less of our native antioxidants.  
>Plant antioxidants are presumably different enough from ours that our 
>body doesn't recognize it.

The fact is that oxygen is a very toxic molecule. If it weren't so
essential for life (and so abundant) the EPA would ban it immediately!
The early cyanobacteria really did pollute the atmosphere with their
wastes -- probably the worst environmental catastrophe in all of
earth's history.

Plants are different from animals in two important ways.  First, they
really are just biochemical machines -- putting all ther energy into
chemistry rather than into producing movement and behavior. But, more
important, they are now the ones producing all that toxic oxygen!  So
they get exposed to a far heavier dose than our own cells.  In fact,
the oxygen level (partial pressure) in most of our cells is really
quite low compared to the level in the atmosphere.  In plant cells, it
can be even higher than atmospheric levels.  So they suffer more from
the harmful effects and have more ways to deal with them. Since
animals are heterotrophs, we can rely on other oganisms to synthesize
some of the essential things we need and count on getting them in our
food rather than synthesizing them for ourselves.
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