membranaires

Membranaires is a term found in some French biological writings to designate organisms whose cells contain extensive internal membranes and membrane-bound organelles. In current usage, the term is largely historical or pedagogical, and the standard term is eucaryotes (organismes eucaryotes). This contrasts with procaryotes (bacteria and archaea), which lack a true nucleus and other membrane-bound compartments.

Typical features include: a defined nucleus enclosed by a nuclear envelope, an endomembrane system consisting of the endoplasmic reticulum and Golgi apparatus, mitochondria, and in many lineages plastids such as chloroplasts; a cytoskeleton enabling complex morphology and intracellular transport; and compartmentalization for specialized metabolism and development. The presence of double-membrane organelles like mitochondria and chloroplasts is explained by the endosymbiotic theory.

Eucaryotes (membranaires) are thought to have arisen through endosymbiosis and subsequent elaboration of internal membranes around 1.5–2 billion years ago. The evolution of the nucleus and endomembrane system allowed greater cellular complexity and, ultimately, multicellularity in many lineages.

Members include animals, plants, fungi, and many protists. Membrane-based compartmentalization underpins diverse life strategies, from rapid signaling in neurons to photosynthesis in plants and storage in vacuoles. Understanding membranaires is central to cell biology and evolutionary biology.

The term remains useful in historical or teaching contexts but is largely superseded in modern biology by eucaryotes.