According to the law of conservation of mass, In a chemical reaction, mass is neither created nor destroyed. In other words, the total mass for the reactants needs to equal the total mass of the products.
<u><em>In photosynthesis the reactants are 6 carbon dioxide, 6 water and sunlight. The mass of these reactants adds to equal the mass of the products, which are 1 glucose and 6 oxygen. </em></u>
<u><em>Cellular respiration on the other hand uses glucose and oxygen gas to produce water, carbon dioxide, and a usable form of energy known as ATP.</em></u>
Cellular respiration is the opposite of photosynthesis, such that the products of photosynthesis are the reactants of cellular respiration. Cellular respiration also obeys the law of conservation of mass.