Chloroplasts are a type of organelle in plant cells that produce the basic sugars. They fix inorganic carbon (CO2), and transform it into organic carbon. Starting from the CO2, chloroplasts produce glucose, using sunlight as a source of energy. This process involves chlorophyll and electron transfer. The products of CO2 fixation can be used either to obtain other organic products (like lipids) or to produce energy (as ATP), both necessary for cell (and plant) survival.