The primary photochemical reaction is the light-dependent reaction of photosynthesis during which light energy is absorbed and converted to the chemical energy of ATP, and NADPH is also synthesized during the process. The photochemical reaction occurs in the thylakoid membranes in which the various photosynthetic pigments and cytochromes are supposed to arrange in the form of paracrystalline, spheroid particles called quantasome.
Quantasomes were first identified by R.B. Pork in 1962. They are chlorophyll-containing spherical granules in the thylakoid membrane of chloroplasts. They are composed of lipids and proteins, and includes various photosynthetic pigments and cytochromes and are the sites of light reaction of photosynthesis. Each quantasome contains about 230 chlorophyll molecules. The quantasomes are of two types- the smaller quantasome which represents the site of photosystem I, and the larger quantasomes which represent the site of photosystem II.