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Why are hydrogen bonds so important for life? Or more generally asked: Why is water so important for life / biological systems? Or maybe again in other words: Why does especially water provide this special property? And not a single other substitute(?) ? I can read what the hydrogen bonds cause to happen but I would rather like to know: Why is that in detail or what makes so water so much different from any other (similar?) liquid?

I know this touches heavily biology (or also physics) but I think I will find the reason in an chemical explanation?

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    $\begingroup$ This is a huge question without a simple answer. H bonds help to hold DNA/RNA and proteins together and so give them structure. Also it may be that it is the polar nature of liquid water (as a large dielectric constant) that is important as this forces many types of molecules to form bilayers (rather than dissolving) and hence vesicles and cells which compartmentalise different molecules. $\endgroup$ – porphyrin May 8 at 7:49
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    $\begingroup$ Hydrogen bonds sure do make supramolecular chemistry more accessible, and life is all about supramolecular chemistry. $\endgroup$ – Nicolau Saker Neto May 8 at 8:24
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Water is (almost) everywhere on earth in copious amounts. It is liquid at earth conditions (H-bridges!). It's rather non-toxic (or organisms were able to evolve to tolerate water well). It is a good solvent for the molecules involved in energy metabolism and biostructure ana- and catabolism. Water has neutral pH, it happily donates and accepts protons which makes it ideal for participation in metabolism.

I'd broaden the question, asking for other molecules that could support life as we know it in a similar way like water does it and also check other liquid molecules which are available in large quantities in the universe (e.g. ammonia, nitrogen, hydrogen) if they could support other forms of life that depend on analogous chemical processes, or even go beyond that (silicon- and aluminum oxides, etc.)

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  • $\begingroup$ The idea that other liquids could support "other forms of life" is science fiction not chemistry as nobody has ever showed how any non-carbon, non-water based chemistry could come remotely close to the complexity required for life. $\endgroup$ – matt_black May 8 at 14:04

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