Photosynthesis and respiration are complementary processes that both involve carbon dioxide, water, glucose and oxygen, and this is what they have in common. Essentially, they are the same reactions, although the reactions occur in reverse. Photosynthesis converts water and carbon dioxide into glucose and oxygen, while respiration converts glucose and oxygen into carbon dioxide and water.
The products of each process serve as reactants to the other. Plants use carbon dioxide to create sugar molecules. They release oxygen which is taken in by animals and broken down into sugar molecules. This process releases carbon dioxide, and the cycle begins again.
The main function of photosynthesis is producing food and capturing energy, while the main function of respiration is breaking down food and releasing energy. In photosynthesis, carbon dioxide and water are combined in the presence of sunlight. Plants, bacteria and fungi use this process to produce sugar. Sunlight is absorbed by the chlorophyll that is found in the chloroplasts of plants. This is where photosynthesis takes place.
In respiration, glucose is broken down into carbon dioxide and water. It is a set of metabolic reactions that occur in the cells of certain living organisms. There are two types of cellular respiration. The first one is aerobic respiration, which requires the use of oxygen, and the second one is anaerobic respiration which does not require oxygen.