why we breathe oxygen and not something like carbon dioxide or nitrogen?

Question

why we breathe oxygen and not something like carbon dioxide or nitrogen?

In: 40

Answer 1

At the very basic level we are machines that consumes sugar for energy. Sugar is made of carbon, hydrogen and oxygen. We convert the sugar into H2O(water) and CO2 to extract the energy in sugar. But there’s not enough oxygen in sugar to complete the reaction. Therefore we breathe in oxygen to facilitate this reaction.