Establish a better understanding of photosynthesis and cellular respiration, and apply the scientific method to solve (or understand) a problem. Photosynthesis and respiration are reactions that complement each other in the environment. They are essentially the same reactions, but they occur in reverse. During photosynthesis, carbon dioxide and water yield glucose and oxygen. Through the respiration process, glucose and oxygen yield carbon dioxide and water. They work well together because living organisms supply plants with carbon dioxide, which undergoes photosynthesis and produces glucose, and these plants and bacteria give out oxygen, which all living organisms need for respiration