Bacterial cell. Illustration of the components of a prokaryotic cell. The structure of the prokaryotes (single-celled organisms such as bacteria and archaea) differs fundamentally from the cells of the eukaryotes (all other living organisms). Prokaryotes lack internal compartments such as a cell nucleus with a membrane to enclose nucleic acids such as deoxyribonucleic acid (DNA, blue). This is a motile bacterium with a flagellum (green, lower right). Other components are pili (green), ribosomes (blue dots), a plasma membrane (red), a cell wall (yellow), and an outer capsule (orange). For this artwork with labels, see image C023/8723.