Prokaryotes are creatures with only one cell. They are often of a single cell type. Nucleolar membranes are absent in prokaryotes. As a result, the cell's nucleus is not well delineated. The nucleolus is missing in prokaryotes because the nucleus is improperly characterised. In addition, not all of the cell organelles are present in prokaryotes. Prokaryotes are therefore defined as cells that contain nuclear components but lack a nuclear membrane. Prokaryotes include many organisms including bacteria and blue-green algae.