It’s the krebs cycle. If you look at how sugar is broken down by the cells to make atp, the actual energy your cells use, it takes C6H12O6 (sugar) and makes it into a few CO2 and H2O, getting energy (atp) from breaking it down into the components. That CO2 is then exhaled, which is I think what OP is referring to.
Note: it’s been a long time since I learned that in class so it is most likely somewhat incorrect












If my memory serves me correctly, there was Adam and Eve (the first people), then they gave birth to Cain and Abel. Then after Cain kills Abel, he gets sent out to live as an outcast amongst “the other people of the world”. … Who? I think someone said one belief is Adam and Eve kept having kids and they became the rest of the people. So yeah, Cain was old.