Furthermore, one or two additional membranes may enclose chloroplasts in organisms that underwent secondary endosymbiosis, such as the euglenids and chlorarachniophytes.

[2] Over millions of years the endosymbiotic cyanobacterium evolved structurally and functionally, retaining its own DNA and the ability to divide by binary fission (not mitotically) but giving up its autonomy by the transfer of some of its genes to the nuclear genome.

[7] These are the sites of light absorption and ATP synthesis, and contain many proteins, including those involved in the electron transport chain.

Photosynthetic pigments such as chlorophylls a,b,c and some others, e.g., xanthophylls, carotenoids, phycobilins are also embedded within the granum membrane.

With exception of chlorophyll a, all the other associated pigments are "accessory" and transfer energy to the reaction centers of Photosytems I and II.