The process of photosynthesis is the method by which plants (and some unicellular bacteria and protists) use the energy provided by the sun to produce glucose, which is converted into simpler sugars during cellular respiration. Photosynthesis involves several complex reactions, each of which plays an important role in the development of glucose and energy exchange. One of the greatest misconceptions about photosynthesis is that the plant converts the energy from the sun directly into glucose. This is not the case.The light captured by chlorophyll is used to produce ATP (adenosine triphosphate) in Photosystem II and Photosystem I, which together are known as the Light Reactions. The Dark Reactions, on the other hand, use the ATP produced initially in the light reactions to drive the process of carbon fixation, better known as the Calvin-Benson (C3) Cycle. They are called dark reactions because they do not need light to operate, although they can occur during the day.