We inhale O2 and exhale CO2, so does that mean we just add carbon and exhale the same oxygen we just inhaled? Why cant we just exhale carbon?
In: Biology
There are obviously practical difficulties of exhaling diamonds or graphite like others have pointed out but this explanation kinda misses the point. Your body doesn’t just have to ‘get rid of carbon somehow’. Just like a fire, your body needs the oxygen in its own right to burn your food and this is which gives us the much-needed energy to live. The global reaction is essentially identical to the one of a fire, although of course the mechanics in our body are much more controlled and complex in order to harvest the energy of this ‘burning’ reaction as good as possible: the food/wood gives its electrons to oxygen, so the food/wood becomes CO2 being depleted of electrons, and there is part of the oxygen getting electrons and becoming water. So yes, besides CO2, the other essential product of fire is water, which may be a bit counter-intuitive.
In a fire part of the oxygen atoms will interact and end up in the CO2 quite directly, but in your body this does not happen directly: the oxygen molecules incorporated in your food while it is getting burned there comes from water molecules which may just as well be the water you drink as the water you produced from the O2 you breathed in, anyways, the net reaction will be the same as in a fire, and the process of burning food will also produce excess water which you will have to breathe out in the form of water vapor. On a cold day you can see how much water vapor you actually breathe out, of which by the way our not very good friend the coronavirus makes good use.
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