Photosynthesis is an anabolic process in which the construction of the bio molecules occurs with the expenditure of ATP. Whereas the cellular respiration is a catabolism process in which the breakdown of bio molecules occurs with the release of ATP. That is photosynthesis builds the organic compounds like carbohydrate by combining the carbon dioxide and water. In complementary to the photosynthesis the respiration breaks the carbohydrates into carbon dioxide and water. So both of these processes are regarded as complementary to each other.
