[eli5] Humans and most animals breathe in O2(dioxide) and breathe out CO2(carbon dioxide) , where does the carbon come from?

Question

[eli5] Humans and most animals breathe in O2(dioxide) and breathe out CO2(carbon dioxide) , where does the carbon come from?

In: Biology

Answer 1

When you eat food you basically put it into little machines inside you, the machines pull apart the food into energy to use, but need oxygen to be able to work properly. When the machines have finished with the food then they have some co2 left, and we breath it out.