A chloroplast is an 11 letter cell organelle found in plants and algae. It is a type of plastid, which are organelles that contain photosynthetic pigments and are the site of photosynthesis. Chloroplasts are responsible for converting light energy into chemical energy, which is then used to produce food for the plant. They are also responsible for producing oxygen as a by-product of photosynthesis. Chloroplasts are typically green in color due to the presence of chlorophyll, which is the pigment responsible for absorbing light energy.