mitochondrial outer membrane

GO:0005741 · Membrane organelle · Membrane · Proposed

The outer, i.e. cytoplasm-facing, lipid bilayer of the mitochondrial envelope. [GO:0005741]

Synonyms: mitochondrion outer membrane; outer mitochondrial membrane; outer mitochondrion membrane

Part of: mitochondrial envelope (GO:0005740)

Has part: mitochondrial outer membrane translocase complex (GO:0005742)

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
mitochondrial outer lipid bilayer	Lipid	part of	Reviewed label only (reviewed name; no accession asserted)			ESSENTIAL	Cytoplasm-facing lipid bilayer that forms the outer boundary of the mitochondrial envelope. `GO:0005741` GO:0005741 defines the mitochondrial outer membrane as the cytoplasm-facing lipid bilayer of the mitochondrial envelope.

NCBITaxon:2759 Eukaryota — VARIABLE: Canonical mitochondrial outer membranes occur with canonical mitochondria across eukaryotes, while some anaerobic lineages carry reduced mitochondrion-related organelles instead. [GO:0005741]
NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding-yeast mitochondria include outer-membrane proteins and outer-membrane import machinery. [DOI:10.1073/pnas.2135385100]

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model used for purified mitochondrial proteomics and for analysis of mitochondrial protein-import machinery. [DOI:10.1073/pnas.2135385100]

protein import into mitochondrial matrix GO:0030150 — Outer-membrane TOM translocases provide the entry step for cytosolic precursor proteins that continue into the mitochondrial matrix.
- GO:0005742 GO:0005742 defines the TOM complex as a mitochondrial outer membrane complex that mediates protein transport into mitochondrial compartments.
- DOI:10.1016/j.cell.2009.08.005 Chacinska et al. 2009 review TOM as the outer-membrane entry gate for mitochondrial precursor proteins.

The mitochondrial outer membrane is the cytoplasm-facing mitochondrial envelope bilayer and hosts the TOM complex that gates protein import.

Subject	Predicate	Object	Evidence
mitochondrial outer membrane	is part of	mitochondrial envelope	`GO:0005741` GO:0005741 defines the outer membrane as the outer lipid bilayer of the mitochondrial envelope.
mitochondrial outer membrane	faces	cytoplasm	`GO:0005741` GO:0005741 identifies this envelope bilayer by its cytoplasm-facing orientation.
mitochondrial outer membrane	bounds	mitochondrial intermembrane space	`GO:0005758` GO:0005758 defines the intermembrane space as the region between the inner and outer lipid bilayers of the mitochondrial envelope.
mitochondrial outer membrane translocase complex	spans	mitochondrial outer membrane	`GO:0005742` GO:0005742 places the TOM complex in the mitochondrial outer membrane.
mitochondrial outer membrane translocase complex	provides entry for	protein import into mitochondrial matrix	`DOI:10.1016/j.cell.2009.08.005` Chacinska et al. 2009 review TOM entry and downstream TIM23-PAM presequence import into the mitochondrial matrix.

CURATION_TODO (OPEN): Resolve an exact source-neutral grounding for the lipid constituent of the mitochondrial outer membrane. GO:0005741 identifies the whole mitochondrial outer membrane, but the lipid-bilayer constituent is intentionally left as reviewed-label-only until an exact source-neutral lipid or membrane-constituent CURIE is curated.

GO:0005741 Gene Ontology cellular-component term for mitochondrial outer membrane.
GO:0031968 Gene Ontology cellular-component parent term for organelle outer membrane.
GO:0031966 Gene Ontology cellular-component parent term for mitochondrial membrane.
GO:0005740 Gene Ontology cellular-component term for the mitochondrial envelope.
GO:0005742 Gene Ontology cellular-component term for the mitochondrial outer membrane translocase complex.
GO:0005737 — cytoplasm Gene Ontology cellular-component term for cytoplasm.
GO:0005758 Gene Ontology cellular-component term for mitochondrial intermembrane space.
GO:0030150 Gene Ontology biological-process term for protein import into the mitochondrial matrix.
DOI:10.1016/j.cell.2009.08.005 Chacinska et al. 2009, 'Importing mitochondrial proteins: machineries and mechanisms', Cell.
DOI:10.1073/pnas.2135385100 Sickmann et al. 2003, 'The proteome of Saccharomyces cerevisiae mitochondria', Proceedings of the National Academy of Sciences.
DOI:10.1038/nature12985 Friedman and Nunnari 2014, 'Mitochondrial form and function', Nature.

2026-09-13T23:50:44Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-13T23:51:54Z codex · EXPANDED_RECORD — Added GO parentage, mitochondrial-envelope parthood, TOM containment, a reviewed-label-only lipid-bilayer component, Eukaryota and Saccharomyces scope, protein-import function evidence, a nonmechanistic outer-membrane topology graph, and a lipid-bilayer grounding TODO.