Explore the world of prokaryotic cells—simple, single-celled organisms lacking a nucleus and membrane-bound organelles. Prokaryotes, mainly bacteria and archaea, come in various shapes and sizes. Key components include circular DNA in the nucleoid, ribosomes, and sometimes plasmids. Their cell structure includes a protective cell wall, made of peptidoglycan in bacteria or pseudomurein in archaea, and a phospholipid bilayer plasma membrane, which controls molecule movement and provides cellular structure. Unique to prokaryotes, Gram-negative bacteria also feature an outer membrane. Movement and attachment are facilitated by flagella, pili, fimbriae, and a slime capsule, supporting both mobility and colony formation. Prokaryotic cells play essential roles in ecological processes, disease, and scientific research.