Question

If we take in OXYGEN and breathe out CARBON DIOXIDE then how does our body breathe in onli oxygen only?

Answer 1

When we breathe in air, all the gases enter in our lungs. But in red blood cells, hemoglobin is present there. And it can bind only with oxygen, not with other gases. Now oxidation reactions occur in cell which give out carbon-dioxide gas. As all other gases also come out during exhaling, but concentration of carbon-dioxide gas is major, this is the reason we say that, we exhale carbon-dioxide.

Nitrogen gas, which is inhaled is not involved in protein synthesis. Protein in the body is synthesized by only food, which we eat.