part_of part of part of intracellular anatomical structure membrane-bounded organelle intracellular organelle intracellular membrane-bounded organelle Organized structure of distinctive morphology and function, bounded by a single or double lipid bilayer membrane and occurring within the cell. Includes the nucleus, mitochondria, plastids, vacuoles, and vesicles. Excludes the plasma membrane. cellular_component intracellular membrane-enclosed organelle GO:0043231