Eukaryotic cells share several distinctive features, such as: the cytoplasm within specialized organelles such as the mitochondria, the chloroplast, the Golgi complex, both a rough and smooth endoplasmic reticulum, a nuclear envelope that isolates DNA from the cytoplasm and an endomembrane system that provides structure and function to the cell's organelles. Both the mitochondrion and the chloroplast are energy transducing organelles, meaning that they transform energy from one form to another, and are believed to have evolved from free-living prokaryotes, as supported by the theory of endosymbiosis. This theory suggests that folding of the plasma membrane coupled with the uptake of prokaryotic cells by other prokaryotes could evolve into a later, more complex and specialized cell type and is demonstrated by related morphological features such as between cytobacteria and chloroplasts and between mitochondria and aerobic prokaryotes. Further evidence includes reproduction of mitochondria and chloroplasts through binary fission as in prokaryotes, the presence of DNA in both free-living prokaryotes and energy-transducing organelles (apart from the nucleus), protein synthesis, and the presence of enzymes and ribosomes where the ribosomes of prokaryotes are located. comparable to those of mitochondria and chloroplasts,