On May 13, 2014, at 9:20 PM, Tim <xxxxxx@little-possums.net> wrote:

> On Wed, May 14, 2014 at 01:53:00PM +1000, Tim wrote:
>> I don't see any particular reason why they would, apart from a
>> tendency in fiction toward "silicon occurs mostly in rocks on Earth,
>> therefore anything with silicon in it must be hard and rocky".
>
> Following up on this a little, it might also be interesting to ponder
> why many of Earth's so-called "carbon-based" organisms use various
> calcium, phosphate, and/or protein structures for hard or tough parts,
> and none at all use stronger (and more carbonaceous) diamond or
> carbon-fibre structures.

Biological organisms cannot generate the heat and pressures to create a diamond (although one that could would make for a really fierce dragon!), and carbon-fiber creation is essentially impossible to manage with enzymes.

(proteins really want ‘sticky’ bits to grab onto, positive or negatively charged atoms connected to the neutral carbon chain. )

Calcium and phosphate salts are enormously available in solution in water, and have the requisite ionic ‘stickyness' for enzymes to do their thing.

Biological organisms can’t really do anything with plain carbon.

--
Bruce Johnson
University of Arizona
College of Pharmacy
Information Technology Group

Institutions do not have opinions, merely customs