Green plants (producers) can use light energy to make their own food. This process is called photosynthesis. General purpose of this lecture is to present on Leaf Structure and Photosynthesis. Green plants are green because they contain a chemical called chlorophyll. This chemical is used to trap light energy. Chlorophyll is contained in the chloroplasts of plant cells. Light energy is used to change carbon dioxide and water into starch and oxygen. The word equation for photosynthesis is: carbon + water ——-→ starch + oxygen dioxide.