Where does the carbon dioxide that we exhale come from?

1 Answer
Aug 2, 2017

From cellular metabolism.


When we breathe in oxygen, blood transports the oxygen along with other nutrients to all parts of the body.

At the cellular level, this oxygen is used to oxidise glucose which is the body's primary energy source. The byproducts of this metabolism are water and carbon dioxide which is exhaled.

This link gives a more detailed explanation:
Why Do We Inhale Oxygen And Exhale Carbon Dioxide?