An apicoplast is a derived non-photosynthetic plastid found in most Apicomplexa, including malaria parasites such as Plasmodium falciparum, but not in others such as Cryptosporidium. It originated from an alga (there is debate as to whether this was a green or red alga) through secondary endosymbiosis. The apicoplast is surrounded by four membranes within the outermost part of the endomembrane system.