What four substances are recycled during photosynthesis & respiration?

What four substances are recycled during photosynthesis and respiration ?

Answer:

Photosynthesis and respiration both recycle four substances: glucose, water, carbon dioxide, and oxygen. Energy, however, cannot be recycled, and energy must continually be supplied by the sun. The products of photosynthesis are the reactants for respiration, and the products of respiration provide the reactants for photosynthesis, thus creating a cycle. Photosynthesis uses sunlight energy to convert carbon dioxide and water into glucose and oxygen. The glucose and oxygen, when metabolized, produce carbon dioxide and water. This circular cycle is essential to sustain humans, animals, and plants and keep life rolling on Earth.