Question

Do the atoms of oxygen in exhaled carbon dioxide come from the atoms in inhaled molecular oxygen (O2)? Explain.

Answer 1

No,They are not the same inhaled oxygen atoms

Here we are talking about cellular respiration

the net equation which we write is

C₆H₁₂O₆+6O₂ = 6CO₂ + 6H₂O + energy

Now lets talk about all these substituents

We get important nutrients like fats,carbohydrates and proteins from food that we eat which gets stored in form of glycogen which later converts to Glucose(C₆H₁₂O₆) which later gets converted into simpler carbon compounds by the process of Glycolysis.Later By Kreb's cycle these compounds are used to produce multiple molecules of CO₂ and energy.After that the oxygen which we intake is used in Electron Transport chain getting oxygen converted to O^2- which with fusion with Hydrogen ions creates H₂O.

Thus the exhaled carbon dioxide doesnt have the same oxygen atoms that we inhaled.

Summary:

The oxygen we inhale gets reduced and gets converted into H₂Oand then something has to be oxidised so glucose at last gets oxidised into carbon dioxide that we exhale.