| Description | A location, relative to cellular compartments and structures, occupied by a macromolecular machine. There are three types of cellular components described in the gene ontology: (1) the cellular anatomical entity where a gene product carries out a molecular function (e.g., plasma membrane, cytoskeleton) or membrane-enclosed compartments (e.g., mitochondrion); (2) virion components, where viral proteins act, and (3) the stable macromolecular complexes of which gene product are parts (e.g., the clathrin complex). |
| Comment | Note that, in addition to forming the root of the cellular component ontology, this term is recommended for the annotation of gene products whose cellular component is unknown. When this term is used for annotation, it indicates that no information was available about the cellular component of the gene product annotated as of the date the annotation was made; the evidence code 'no data' (ND), is used to indicate this. |