The Chemistry of Life

The inability of hydrogen to bond to oxygen would eliminate water which I think is elemental to all life as we know it, right?

Chemical life as we know it Jim, yes.

Some life forms don't need much, but they all need some ... am I correct? I mean, in addition to the basic need of water in DNA.

Yes, life as we know it -- the cell -- needs a solvent to live in, to handle things like getting other molecules (food) and disposing of molecules (waste). Liquids are best for this solvent as they give the opportunity for molecules to encounter eachother, solids are too rigid to generally allow this and the encounters between gas molecules are too infrequent for the rate of information transfer required. Water is ideally suited as a solvent for life for lots of reasons, and it's made of two of the most abundant elements found in the Universe. You probably know more than I do about this stuff having read that book on the cell :-)

Question: is possession of DNA a definition of "life?" Some things -- simple viruses for instance -- have RNA but not DNA, correct?

Correct, an example is the influenza virus, it has RNA as it's basic material - it's "genome" is based on RNA. The HIV virus also has an RNA based genome but manufactures DNA from this RNA, so it's a retrovirus, by definition. Life without DNA is possible for sure.

Are they considered "life?" Do all plants and animals have DNA, including things like fungus and lichen?

Yes I think virii and retrovirii are considered "life", they respond and adapt to their environment after all. Looking back at my old definition of human nature in our blog I see:

1. We learn through response to stimuli
2. Once we've learned something we have a preference for it over something that we haven't learned (ie. We prefer the familiar to the unfamiliar)

I think this pretty much sums up my view of what "life" is too. Note that "artificial life" or "non-chemical life" -- computers, machines etc might be able to do the same one day.

All plants and animals have DNA, to my knowledge.

The lack of carbon means the elimination of complex molecular strings, does it not? Isn't carbon one of the basic things that allow long chains?

Well, because of the strength of the carbon double bond there really isn't anything yet found that could act as a better elemental building block for life. Silicon has been posited as being a second candidate as it has some similar properties to carbon, but comes in a distant second to carbon when you look at it's chemical suitability for the job.

You have a Periodic Table on your wall? You do? Seriously?

Oh yes !

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How is the motorcycle working out? You know the fab four, The Beatles, got their name from a biker film starring Marlon Brando? Are you a fully paid up member of the Tucson Chapter of Hells Angels yet?

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My daughter has a friend over for a sleepover tonight and they are still awake and playing with Shelly the hampster (at 00:33!) I'm about to put my foot down ... :-)