Flexi Says: Comparing photosynthesis and cellular respiration, the similarity between the two processes is striking. Both are processes within the cell which make chemical energy available for life. Photosynthesis transforms light energy into chemical energy stored in glucose, and cellular respiration releases the energy from glucose to build ATP, which does the work of life. Moreover, photosynthesis reactants CO2 and H2O are products of cellular respiration. And the reactants of respiration, C6H12O6 and O2, are the products of photosynthesis.