This (from another article<http://www.the-scientist.com/news/display/57851/#ixzz16zxXUGXe>) looks like a significant part of the answer.
Arsenic falls directly below phosphorus on the period table, and thus has many similar chemical properties. In contrast to relatively stable phosphorus-based molecules, however, arsenic compounds are extremely unstable. While phosphorus compounds take years, decades, or even millennia to break down, the rate of hydrolysis of arsenic compounds is usually measured in seconds or minutes. In fact, its similarity to phosphorus and its instability partly explains why arsenic is so toxic. The body may not be able to distinguish between phosphate -- the most common form of phosphorus in organisms -- and its arsenic equivalent, arsenate. As a result, scientists suspect that arsenate can be incorporated into molecules and pathways that normally use phosphate, causing downstream processes to fail if the arsenate molecules are quick to break down or otherwise don't work properly. *-- Russ Abbott* *_____________________________________________* * Professor, Computer Science California State University, Los Angeles Google voice: 424-235-5752 (424-cell-rja) blog: http://russabbott.blogspot.com/ vita: http://sites.google.com/site/russabbott/ _____________________________________________* On Thu, Dec 2, 2010 at 2:56 PM, Russ Abbott <[email protected]> wrote: > Other than the fact that this is the first time we have seen a life form > that uses arsenic as a chemical building block, why is this important? Is > there something about arsenic that is so incompatible with other forms of > life that it would seem to be impossible to do this? > * > -- Russ Abbott > _____________________________________________* > * Professor, Computer Science > California State University, Los Angeles > > Google voice: 424-235-5752 (424-cell-rja) > blog: http://russabbott.blogspot.com/ > vita: http://sites.google.com/site/russabbott/ > _____________________________________________* > > > > On Thu, Dec 2, 2010 at 11:25 AM, glen e. p. ropella <[email protected] > > wrote: > >> >> I presume most of you've seen this already, but just in case: >> >> >> http://www.nasa.gov/topics/universe/features/astrobiology_toxic_chemical.html >> >> "Researchers conducting tests in the harsh environment of Mono Lake in >> California have discovered the first known microorganism on Earth able >> to thrive and reproduce using the toxic chemical arsenic. The >> microorganism substitutes arsenic for phosphorus in its cell components." >> >> -- >> glen e. p. ropella, 971-222-9095, http://tempusdictum.com >> >> >> ============================================================ >> FRIAM Applied Complexity Group listserv >> Meets Fridays 9a-11:30 at cafe at St. John's College >> lectures, archives, unsubscribe, maps at http://www.friam.org >> > >
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