The most common form of plastid, the chloroplast is a photosynthetic organelle found in all photosynthetic eukaryotes except glaucocystophyte algae, where this organelle is called a cyanelle, and Paulinella chromatophore where it is called a chromatophore. In green (photosynthesizing) tissue they house the machinery necessary for pigment biosynthesis, amino acid synthesis, lipid metabolism etc, as well as the machinery for photosynthesis and CO(2) fixation. They are surrounded by between 2 and 4 membranes and contain thylakoids in green tissue.
