[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

The use of the term “dioxide” in the original question intrigued me, so I looked it up…
I think O² is actually called [Dioxygen](https://en.m.wikipedia.org/wiki/Allotropes_of_oxygen#Dioxygen) rather than “dioxide”. An oxide is always going to be a compound, formed with at least one other element.