#5
by Calilasseia » Jan 26, 2017 6:35 pm
First of all, water doesn't rot. Rotting is the degradation of proteins and lipids in corpses (or other previously live, now dead, organic material) by bacteria. The bacteria responsible for the early stages of this process utilise protease enzymes to cleave the peptide bonds in proteins, and other enzymes to metabolise the lipids, and those enzymes may or may not have a restricted range of pH within which they are functional. Whilst the cleaving of peptide bonds by proteases involves hydrolysis - the process of separating a water molecule into H+ and OH- ions, prior to those ions being attached to the now-broken ends of a severed peptide bond, this process doesn't constitute "rotting" of the water. Basically, if you have a peptide bond, the reaction is as follows:
R-CO-NH-R' + H2O -> R-COOH + R'-NH2
Digestion of food involves the same reaction, which is why digestion requires an input of at least enough water to provide the reaction water for the hydrolysis reactions that will eventually convert proteins into free amino acids. But of course, when the reverse reactions take place in your body, and those free amino acids are assembled into the proteins your cells require for their functioning, those reverse reactions liberate water molecules, and those water molecules now present an osmoregulatory problem. The same happens within those bacteria once they've absorbed any free amino acids liberated by protease activity, and reassembled them into bacterial proteins - they now have a water surplus to process.
But, at bottom, one water molecule is pretty much indistinguishable from any other water molecule, unless deuterium or 18O isotopes enter the picture. Individual water molecules don't acquire any mystical 'taint' because they've passed through the metabolism of an organism, which is just as well, because if they did, we'd be drinking some pretty nasty stuff after 3.5 billion years of biosphere metabolic activity.
The idea that water somehow magically acquires additional properties, because the water molecules were previously in contact with something else, is straight out of the homeopathy woo book, unless of course that something else happens to be a radioactive neutron source, resulting in the conversion of the constituent hydrogen and oxygen atoms to radioactive isotopes. Though even if that happens, tritium will decay to 3He, at which point said water molecule will cease to be one, and likewise, if 19O is formed, this will decay to 19F, which itself will very quickly find a chemical partner to react with, and your water molecule will cease to be one yet again.
Then, there's the little matter of the energy required to perform an electrolysis of water. If your water sample is pure, then there's a large activation energy barrier to overcome in order to start the electrolysis, and the electrolysis proceeds slowly, unless you bring a lot of energy to bear. But once again, you no longer have water molecules as your products.
Usually, the activation energy barrier is circumvented via using an electrolyte, but that complicates the reaction picture immediately, because competing side reactions can occur. Dissolve standard table salt, which is mostly NaCl, in water beforehand, then passing an electric current through that, will usually result in chlorine appearing at the anode, not oxygen. Then there's the matter of whether or not the electrodes are themselves inert or not.
Whee, I just had a crash revision course of my old O level chemistry syllabus.
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