chloroplast

GO:0009507 · Membrane organelle · Membrane bounded organelle · Proposed

A chlorophyll-containing plastid with thylakoids organized into grana and frets, or stroma thylakoids, and embedded in a stroma. [GO:0009507]

Has part: chloroplast envelope (GO:0009941); chloroplast outer membrane (GO:0009707); chloroplast inner membrane (GO:0009706); chloroplast stroma (GO:0009570); chloroplast thylakoid (GO:0009534); chloroplast thylakoid membrane (GO:0009535); Toc complex (GO:0010006); Tic complex (GO:0031897)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Essential	Role
chloroplast outer membrane	Lipid	part of	`GO:0009707`	UNKNOWN	Cytoplasm-facing lipid bilayer of the chloroplast envelope and outer-membrane platform for TOC-dependent preprotein import. `GO:0009707` GO:0009707 defines the chloroplast outer membrane as the cytoplasm-facing lipid bilayer of the chloroplast envelope.
chloroplast inner membrane	Lipid	part of	`GO:0009706`	UNKNOWN	Stroma-facing lipid bilayer of the chloroplast envelope that participates with the outer envelope in delimiting the chloroplast compartment. `GO:0009706` GO:0009706 defines the chloroplast inner membrane as the inner lipid bilayer of the chloroplast envelope facing the stroma.
chloroplast thylakoid membrane	Lipid	part of	`GO:0009535`	UNKNOWN	Pigmented membrane that bounds chloroplast thylakoid cisternae in the chloroplast stroma. `GO:0009535` GO:0009535 defines the chloroplast thylakoid membrane as the pigmented membrane of a chloroplast thylakoid.
TOC-TIC import supercomplex	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)	UNKNOWN	Envelope-spanning translocase that conducts nuclear-encoded preproteins across the outer and inner chloroplast envelope membranes toward the stroma. `DOI:10.1016/j.cell.2022.10.030` Jin et al. 2022 resolved a Chlamydomonas TOC-TIC supercomplex spanning the two chloroplast envelope membranes.

Taxonomic distribution

NCBITaxon:33090 Viridiplantae — COMMON: Green algae and land plants contain primary plastids derived from a cyanobacterial endosymbiont; chlorophyll-containing chloroplasts are widespread in photosynthetic members of the clade. [DOI:10.1098/rstb.2009.0103]
NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: The unicellular green alga Chlamydomonas reinhardtii contains a chloroplast with envelope, stroma, and thylakoid compartments used for photosynthesis and chloroplast protein biogenesis studies. [DOI:10.1007/s00294-011-0339-1]

Canonical examples

NCBITaxon:3055 Chlamydomonas reinhardtii — Unicellular green-algal model used to compare the Chlamydomonas chloroplast proteome and metabolic repertoire with plant chloroplasts. [DOI:10.1007/s00294-011-0339-1]

Functions

photosynthesis GO:0015979 — Chloroplast thylakoid membranes and stromal enzymes convert light energy and carbon dioxide into organic carbon through photosynthetic electron transport and carbon fixation.
- GO:0015979 GO:0015979 defines photosynthesis as synthesis of organic compounds from CO2 using light energy.
- DOI:10.1007/s00294-011-0339-1 Terashima, Specht and Hippler 2011 review the Chlamydomonas chloroplast proteome, including thylakoid photosynthetic complexes and stromal metabolism.
protein import into chloroplast stroma GO:0045037 — Envelope translocases import nucleus-encoded precursor proteins across the chloroplast outer and inner membranes to reach the stroma.
- GO:0045037 GO:0045037 defines protein import into the chloroplast stroma.
- DOI:10.1016/j.cell.2022.10.030 Jin et al. 2022 determined a Chlamydomonas TOC-TIC structure that spans the chloroplast envelope and forms a pathway for preprotein translocation.

Mechanism graphs

Chloroplast envelope and thylakoids organize import (FUNCTION)

In Chlamydomonas, two envelope membranes bound the chloroplast stroma, thylakoid membranes provide internal photosynthetic compartments, and a TOC-TIC supercomplex spans both envelope membranes during protein import.

Subject	Predicate	Object	Evidence
chloroplast envelope	encloses	chloroplast	`GO:0009941` GO:0009941 defines the chloroplast envelope as the double lipid bilayer enclosing the chloroplast.
chloroplast outer membrane	is part of	chloroplast envelope	`GO:0009707` GO:0009707 places the chloroplast outer membrane in the chloroplast envelope.
chloroplast inner membrane	is part of	chloroplast envelope	`GO:0009706` GO:0009706 places the chloroplast inner membrane in the chloroplast envelope.
chloroplast envelope	bounds	chloroplast stroma	`GO:0009570` GO:0009570 defines the stroma as the space enclosed by the double membrane of a chloroplast but excluding the thylakoid space.
chloroplast thylakoid	is embedded in	chloroplast stroma	`GO:0009507` GO:0009507 defines chloroplasts as chlorophyll-containing plastids with thylakoids embedded in a stroma.
chloroplast thylakoid membrane	bounds	chloroplast thylakoid	`GO:0009535` GO:0009535 defines the chloroplast thylakoid membrane as the pigmented membrane of a chloroplast thylakoid.
TOC-TIC import supercomplex	spans	chloroplast envelope	`DOI:10.1016/j.cell.2022.10.030` Jin et al. 2022 resolved a TOC-TIC supercomplex spanning the two Chlamydomonas chloroplast envelope membranes.
TOC-TIC import supercomplex	mediates	protein import into chloroplast stroma	`DOI:10.1016/j.cell.2022.10.030` Jin et al. 2022 describe a preprotein translocation path connecting the TOC and TIC portions of the Chlamydomonas supercomplex.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral component boundaries and groundings for the chloroplast TOC-TIC import supercomplex, Toc outer-membrane complex, Tic inner-membrane complex, Ycf2/FtsHi ATPase, chloroplast genome, chloroplast ribosome, photosystems, and ATP synthase. This first chloroplast record grounds the envelope membranes and avoids treating the Chlamydomonas TOC-TIC supercomplex, photosynthetic complexes, chloroplast DNA, or chloroplast ribosomes as a single source-neutral component until exact component boundaries are curated.

Evidence

GO:0009507 Gene Ontology cellular-component term for chloroplast.
GO:0009536 Gene Ontology cellular-component term for plastid.
GO:0009941 Gene Ontology cellular-component term for the chloroplast envelope.
GO:0009707 Gene Ontology cellular-component term for the chloroplast outer membrane.
GO:0009706 Gene Ontology cellular-component term for the chloroplast inner membrane.
GO:0009570 Gene Ontology cellular-component term for the chloroplast stroma.
GO:0009534 Gene Ontology cellular-component term for the chloroplast thylakoid.
GO:0009535 Gene Ontology cellular-component term for the chloroplast thylakoid membrane.
GO:0010006 Gene Ontology cellular-component term for the Toc complex.
GO:0031897 Gene Ontology cellular-component term for the Tic complex.
GO:0015979 Gene Ontology biological-process term for photosynthesis.
GO:0045037 Gene Ontology biological-process term for protein import into the chloroplast stroma.
DOI:10.1098/rstb.2009.0103 Keeling 2010, 'The endosymbiotic origin, diversification and fate of plastids', Philosophical Transactions of the Royal Society B.
DOI:10.1007/s00294-011-0339-1 Terashima, Specht and Hippler 2011, 'The chloroplast proteome: a survey from the Chlamydomonas reinhardtii perspective with a focus on distinctive features', Current Genetics.
DOI:10.1016/j.cell.2022.10.030 Jin et al. 2022, 'Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes', Cell.

Curation history

2026-09-11T19:12:20Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-11T19:13:35Z codex · EXPANDED_RECORD — Added plastid parentage, chloroplast envelope and thylakoid part terms, outer/inner/thylakoid membrane and TOC-TIC components, Viridiplantae and Chlamydomonas taxonomic scope, photosynthesis and stromal protein-import functions, a nonmechanistic envelope-and-import graph, and a TOC-TIC grounding TODO.
2026-09-11T19:21:29Z codex · REVIEW_FIXES — Resolved review findings by connecting the chloroplast thylakoid membrane component in the graph, narrowing the Chlamydomonas canonical-example note to its direct proteome evidence, and removing an unused Sun et al. 2025 record-level citation.
2026-09-20T21:55:39Z codex · ADDRESSED_REVIEW — Retyped the chloroplast TOC-TIC import supercomplex graph node as STRUCTURE.

Source: data/structures/membrane_organelle/chloroplast.yaml