Question

If I inhale air I take the 02 from the air. If I than exhale I exhale C02. Where does the C come from? From the air? I read that there is just a tiny part of C in the air.

Answer 1

the C comes from glucose, which you get from what you eat. In the mitochondria, the oxygen you breathe in reacts with glucose to form CO2, water, and energy. The overall reaction is \[C _{6} H _{12} O _{6} + 6O _{2} \rightarrow 6CO _{2} + 6H _{2} O + ATP (energy)\]