chloroplast outer membrane

GO:0009707 · Membrane organelle · Membrane · Proposed

The cytoplasm-facing lipid bilayer of the chloroplast envelope. [GO:0009707]

Synonyms: chloroplastic outer membrane

Part of: chloroplast envelope (GO:0009941)

Xrefs: uniprot.location:SL-0054 — Chloroplast outer membrane

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
chloroplast 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 chloroplast envelope. `GO:0009707` GO:0009707 defines the chloroplast outer membrane as the cytoplasm-facing lipid bilayer of the chloroplast envelope. `uniprot.location:SL-0054` — Chloroplast outer membrane UniProt SL-0054 maps directly to GO:0009707 and describes the chloroplast outer membrane as facing the cytoplasm.

NCBITaxon:33090 Viridiplantae — COMMON: Photosynthetic green algae and land plants carry chloroplasts bounded by chloroplast envelopes with outer membranes. [DOI:10.1098/rstb.2009.0103]
NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: Chlamydomonas reinhardtii has a chloroplast outer membrane carrying the Toc side of the TOC-TIC import supercomplex. [DOI:10.1016/j.cell.2022.10.030]

NCBITaxon:3055 Chlamydomonas reinhardtii — Green-algal model used for structural analysis of a TOC-TIC supercomplex that spans the chloroplast outer and inner envelope membranes. [DOI:10.1016/j.cell.2022.10.030]

The chloroplast outer membrane is the cytoplasm-facing lipid bilayer of the chloroplast envelope and bounds the intermembrane space.

Subject	Predicate	Object	Evidence
chloroplast outer membrane	is part of	chloroplast envelope	`GO:0009707` GO:0009707 defines this outer membrane as a lipid bilayer of the chloroplast envelope. `uniprot.location:SL-0054` — Chloroplast outer membrane UniProt SL-0054 places the chloroplast outer membrane under plastid outer membrane.
chloroplast outer membrane	faces	cytoplasm	`GO:0009707` GO:0009707 identifies this chloroplast envelope bilayer by its cytoplasm-facing orientation. `uniprot.location:SL-0054` — Chloroplast outer membrane UniProt SL-0054 describes the same cytoplasm-facing chloroplast membrane.
chloroplast outer membrane	bounds	chloroplast intermembrane space	`GO:0031972` GO:0031972 identifies the chloroplast intermembrane space as the region between the inner and outer chloroplast membranes.

CURATION_TODO (OPEN): Resolve an exact source-neutral grounding for the lipid constituent of the chloroplast outer membrane. The record is exactly grounded to GO:0009707 and UniProt SL-0054, but the lipid bilayer constituent is intentionally left as a reviewed-label-only component until an exact source-neutral lipid or membrane-constituent CURIE is curated.

GO:0009707 Gene Ontology cellular-component term for chloroplast outer membrane.
GO:0009527 Gene Ontology cellular-component term for plastid outer membrane.
GO:0031969 Gene Ontology cellular-component term for chloroplast membrane.
GO:0009941 Gene Ontology cellular-component term for chloroplast envelope.
GO:0031972 Gene Ontology cellular-component term for the chloroplast intermembrane space bounded by the outer membrane.
GO:0005737 — cytoplasm Gene Ontology cellular-component term for the cytoplasm faced by the outer chloroplast membrane.
uniprot.location:SL-0054 — Chloroplast outer membrane UniProt Subcellular Location entry SL-0054 maps Chloroplast outer membrane to GO:0009707 and places it under both chloroplast membrane and plastid outer membrane.
DOI:10.1098/rstb.2009.0103 Keeling 2010, The endosymbiotic origin, diversification and fate of plastids, Philosophical Transactions of the Royal Society B.
DOI:10.1016/j.cell.2022.10.030 Jin et al. 2022, Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes, Cell.

2026-09-13T02:53:41Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-13T02:54:19Z codex · EXPANDED_RECORD — Added the UniProt SL-0054 xref, plastid outer membrane parentage, chloroplast-envelope parthood, a reviewed-label-only outer lipid bilayer component, Viridiplantae and Chlamydomonas scope, a nonmechanistic boundary graph, and a lipid-bilayer grounding TODO.
2026-09-13T03:00:48Z codex · ADDRESS_REVIEW — Resolved #742 by adding the missing GO:0031969 chloroplast membrane parent and evidence.