Chloroplast is an organelle, similar to
erythrocyte in its size (5 to 10 microns in diameter). Its shape resembles double-convex lens. Chloroplast is a membrane complex. It consists of double outer membrane and creasy inner membranes arranged in stacks of disks. These disks, called
thylakoids, contain components of photosynthesizing apparatus. Chloroplast is the main site for
ATP synthesis in plants.