In the study of biochemistry and
physiology one soon finds that nearly everything that happens in your
body depends on particular chemical reactions. In some ways this is
rather like the study of mechanics; it would be equally reasonable to
ask why we put petrol in our car's fuel tank, or grease into its
lubrication system, and water into its cooling system, instead of water
into the fuel tank, sand into the lubrication, and grease into the
cooling system. Why so fussy?
You know perfectly well (I hope!) why that is: our cars cannot burn
water for fuel, they cannot use sand for lubrication, and grease would
not work well in the cooling system. They cannot do that sort of thing
because those materials have the wrong qualities for those functions.
Now, in the body a major part of the function of oxygen is to attract
and hold onto electrons. A gas like say, carbon dioxide, nitrogen, or
argon, although plentiful, does not attract and hold onto electrons to
any useful degree in the necessary circumstances inside the body. The body is in many ways far fussier about which materials to use than a car is!
Much as some cooling systems could (just about!) get some coolant
effect from grease, but not enough, and one would get some damaging
effects as well, so, if we used other gases such as nitrogen dioxide,
chlorine or fluorine, gases that, much like oxygen, can hold onto
electrons, we would quickly find that not only would they not work as
they should, but they would rapidly cause painful damage that would soon
prove fatal if you did not stop it.
If you don't believe me, ask anyone who has experienced a faceful of chlorine!
