Cellular respiration is the process by which cells obtain energy from glucose. It can be represented by a chemical reaction which, when balanced, obeys the Law of Conservation of Matter:
`C_6H_12O_6 + 6 O_2 -> 6 CO_2 + 6H_2O`
Th number of atoms of reactants equals the number of atoms of products:
six carbon atoms, 12 hydrogen atoms, 18 oxygen atoms
No atoms are created or destroyed in this process, they're just rearranged into different molecules.
We often hear the term "burn" to describe glucose being used by living things for energy. When a substance burns, matter is conserved. It might seem like the burned substance is completely consumed because the products, CO2 and water, are both produced in the gaseous form and are colorless and invisible. The French chemist Antoine Lavoisier was the first to show that mass is conserved in chemical reactions by carrying out combustion reactions in a closed system and capturing the gaseous products.