chloroplast

Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.

Chloroplasts are green because they contain the chlorophyll pigment. Chloroplasts are members of a class of organelles known as plastids.

Chloroplasts are observable as flat discs usually In land plants, they are, in general, 5 μm in diameter and 2.3 μm thick. The chloroplast is contained by an envelope that consists of an inner and an outer phospholipid membrane. Between these two layers is the intermembrane space. The material within the chloroplast is called the stroma and contains one or more molecules of small circular DNA. It also contains ribosomes. Within the stroma are stacks of thylakoids, the sub-organelles, which are the site of photosynthesis. The thylakoids are arranged in stacks called grana (singular: granum).  A thylakoid has a flattened disk shape.