Photosynthesis makes the glucose that is used in cellular respiration to make ATP. The glucose is then turned back into carbon dioxide, which is used in photosynthesis. While water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.
The products of photosynthesis (glucose and oxygen) are the reactants in cellular respiration. The products of cellular respiration (water and carbon dioxide) are the reactants in photosynthesis.
