Generalized prokaryotic cell. Image: Sinauer Associates, Inc.
A prokaryotic cell is a cell lacking a membrane-bounded nucleus or membrane-bounded organelles. Prokaryotic cells are thus more primitive than eukaryotic cells, which evolved from them. A prokaryotic organism, such as a bacterium, consists of single prokaryotic cell.
A general prokaryotic cell can be considered to have three architectural regions, though not all the components are always present: