Prokaryote

Summary

A prokaryote is a microorganism whose usually single cell lacks a nucleus or other membrane-bound organelles. The word prokaryote comes from the Ancient Greek πρό (pró), meaning "before", and κάρυον (káruon), meaning "nut" or "kernel". In the earlier two-empire system, prokaryotes formed the empire Prokaryota. In the three-domain system, based upon molecular phylogenetics, prokaryotes are divided into two domains: Bacteria and Archaea. A third domain, Eukaryota, consists of organisms with cell nuclei.