Re: Chemical bonding inside living vs non-living things

From: Craig Gerken (cagerken_at_aol.comospamnay)
Date: 12/03/04 

Date: 03 Dec 2004 16:02:58 GMT

>
>I have a couple of questions for learned people on the bio/organic
>chemistry groups.
>
>In elementary chemistry we have ionic and covalent bonds between
>molecules in certain simple compounds like H2O (water, covalent), NaCl
>(sodium chloride salt, ionic), and so on where electrons are shared or
>charged ions hold the thing together.
>
>Inside very simple microrganisms clearly things are much more complex,
>since you have long chains of carbon-based organic molecules forming
>the core DNA material along with the broader limbs and organs of the
>living thing. So inside living things do organic compounds go through
>the same kinds of chemical bonding as non-living things (ionic,
>covalent, etc)? What makes something "alive" compared to "non-living"
>when they have the SAME kinds of chemicals inside them?
>
>(PS: Don't tell me if we knew that, we'd have solved the puzzle of
>life...!)
>
>Further question I have is what are the 3 or 4 top elements making up
>a bacterium? Example: 80% carbon, 10% hydrogen, 5% oxygen, 5%
>phosphorus, etc...? What are the 3 or 4 top elements making up the DNA
>double helix inside a bacterium?
>
>Thanks for all thoughts...
>
>Abdul Ahad
>

Abdul,

I can't add much to what has already been said, especially by Trond Erik.
However, in the 19th century "vitalism" was a popular belief, centering around
ideas that you have expressed - that there is something "special" about living
things, and their chemistry must be qualitatively different. This was the
origin of the term "organic" chemistry, out of the belief that organic/living
things worked differently. One of the key experiments that caused vitalism to
fall out of favor was performed by Friedrich Woehler. Basically, he started
with a pile of ammonium cyanate (NH4CNO), a "dead" inorganic salt by anyone's
estimation. He heated the salt, and eventually it transfomed into urea
(NH2CONH2). Urea is, of course, a common waste excreted by living things (a
component of urine). Prior to this, the only known source of urea had been,
well, you know ... It was said of Woehler's "miraculous" discovery that he had
produced urea "without benefit of kidney, bladder or dog." Anyway, the
historical significance of this experiment speaks directly to your question.

Nowadays, we generally believe that what is "special" about life is not so much
its chemistry as its complexity. The elements (C,H,O,N,P,S, and others) behave
just the same as they do in non-living contexts. However, the organization of
the atoms, molecules, cells, etc. is extremely complex.

Without trying to stir up too much controversy, let me suggest that the
relationship of chemistry to biology is similar to that between physics and
chemistry. Physics has laid down the basic principles. One could say that all
of chemistry is just special cases and worked examples of the Schroedinger
Equation. While this is true in a fundamental sense, try explaining, say, a
precipitation reaction by starting from wave mechanics! The simple phenomena
of quantum mechanics become the special cases of atomic physics (shell
structure, quantum numbers, etc.), which become the special case of carbon
chemistry (Lewis structures, polar bonds, solvent effects, etc.). Organic
chemistry does a pretty good job of summarizing the chemical behavior in most
organic materials, but there are a lot of layers of complexity between there
and quantum physics. Just because you know everything there is to know about
quantum mechanics does not give you a free pass to become a synthetic organic
chemist. :) Similarly, while organic reactions are well understood, the
derivation of biology is not completely obvious. There are an enormous number
of chemical reactions in any living thing, and many large chemicals that
interact in a variety of ways. Biology does not invalidate anything in organic
chemistry, but the complexity is vastly increased.

I hope that makes some sense, particularly in light of what else has already
been written.

- Craig

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