Organelle
Organelle | |
---|---|
Details | |
Pronunciation | /ɔːrɡəˈnɛl/ |
Part of | Cell |
Identifiers | |
Latin | organella |
MeSH | D015388 |
TH | H1.00.01.0.00009 |
FMA | 63832 |
Anatomical terms of microanatomy |
In
(these could be referred to as membrane bound in the sense that they are attached to (or bound to) the membrane).Organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organelles, particularly in eukaryotic cells. They include structures that make up the endomembrane system (such as the nuclear envelope, endoplasmic reticulum, and Golgi apparatus), and other structures such as mitochondria and plastids. While prokaryotes do not possess eukaryotic organelles, some do contain protein-shelled bacterial microcompartments, which are thought to act as primitive prokaryotic organelles;[1] and there is also evidence of other membrane-bounded structures.[2] Also, the prokaryotic flagellum which protrudes outside the cell, and its motor, as well as the largely extracellular pilus, are often spoken of as organelles.
History and terminology
Animal cell diagram | |
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In biology, of bodily organs to microscopic cellular substructures is obvious, as from even early works, authors of respective textbooks rarely elaborate on the distinction between the two.
In the 1830s, Félix Dujardin refuted Ehrenberg theory which said that microorganisms have the same organs of multicellular animals, only minor.[4]
Credited as the first
Types
While most cell biologists consider the term organelle to be synonymous with
The first, broader conception of organelles is that they are membrane-bounded structures. However, even by using this definition, some parts of the cell that have been shown to be distinct functional units do not qualify as organelles. Therefore, the use of organelle to also refer to non-membrane bounded structures such as ribosomes is common and accepted.
- large RNA and protein complexes: ribosome, spliceosome, vault
- large protein complexes: proteasome, DNA polymerase III holoenzyme, RNA polymerase II holoenzyme, symmetric viral capsids, complex of GroEL and GroES; membrane protein complexes: porosome, photosystem I, ATP synthase
- large DNA and protein complexes: nucleosome
- microtubule-organizing center(MTOC)
- cytoskeleton
- flagellum
- nucleolus
- stress granule
- germ cell granule
- neuronal transport granule
The mechanisms by which such non-membrane bounded organelles form and retain their spatial integrity have been likened to liquid-liquid phase separation.[15]
The second, more restrictive definition of organelle includes only those cell compartments that contain
Using this definition, there would only be two broad classes of organelles (i.e. those that contain their own DNA, and have originated from endosymbiotic
- mitochondria (in almost all eukaryotes)
- plastids[18] (e.g. in plants, algae, and some protists).
Other organelles are also suggested[by whom?] to have endosymbiotic origins, but do not contain their own DNA[citation needed] (notably the flagellum – see evolution of flagella).
Eukaryotic organelles
Not all eukaryotic cells have each of the organelles listed below. Exceptional organisms have cells that do not include some organelles (such as mitochondria) that might otherwise be considered universal to eukaryotes.[19] The several plastids including chloroplasts are distributed among some but not all eukaryotes.
There are also occasional exceptions to the number of membranes surrounding organelles, listed in the tables below (e.g., some that are listed as double-membrane are sometimes found with single or triple membranes). In addition, the number of individual organelles of each type found in a given cell varies depending upon the function of that cell.
Organelle | Main function | Structure | Organisms | Notes |
---|---|---|---|---|
cell membrane | separates the interior of all cells from the outside environment (the extracellular space) which protects the cell from its environment. | double-layered, fluid sheet of phospholipids
|
all eukaryotes | |
cell wall | The cell wall is a rigid structure composed of cellulose that provides shape to the cell, helps keep the organelles inside the cell, and does not let the cell burst from osmotic pressure. | various | plants, protists, rare kleptoplastic organisms | |
chloroplast (plastid) | photosynthesis, traps energy from sunlight | double-membrane compartment | plants, algae, rare kleptoplastic organisms | has own DNA; theorized to be engulfed by the ancestral archaeplastid cell (endosymbiosis)
|
endoplasmic reticulum | translation and folding of new proteins (rough endoplasmic reticulum), expression of lipids (smooth endoplasmic reticulum) | single-membrane compartment | all eukaryotes | rough endoplasmic reticulum is covered with ribosomes (which are bound to the ribosome membrane), has folds that are flat sacs; smooth endoplasmic reticulum has folds that are tubular |
flagellum | locomotion, sensory | protein | some eukaryotes | |
Golgi apparatus | sorting, packaging, processing and modification of proteins | single-membrane compartment | all eukaryotes | cis-face (convex) nearest to rough endoplasmic reticulum; trans-face (concave) farthest from rough endoplasmic reticulum |
mitochondrion | energy production from the oxidation of glucose substances and the release of adenosine triphosphate | double-membrane compartment | most eukaryotes | constituting element of the chondriome; has own DNA; theorized to have been engulfed by an ancestral eukaryotic cell (endosymbiosis)[20]
|
nucleus | DNA maintenance, controls all activities of the cell, RNA transcription |
double-membrane compartment | all eukaryotes | contains bulk of genome |
vacuole | storage, transportation, helps maintain homeostasis | single-membrane compartment | all eukaryotes |
Organelle/Macromolecule | Main function | Structure | Organisms |
---|---|---|---|
acrosome | helps spermatozoa fuse with ovum | single-membrane compartment | most animals (including sponges) |
autophagosome | vesicle that sequesters cytoplasmic material and organelles for degradation | double-membrane compartment | all eukaryotes |
centriole | anchor for cytoskeleton, organizes cell division by forming spindle fibers | Microtubule protein | animals |
cilium | movement in or of external medium; "critical developmental signaling pathway".[21] | Microtubule protein | animals, protists, few plants |
cnidocyst | stinging | coiled hollow tubule | cnidarians |
eyespot apparatus | detects light, allowing phototaxis to take place | euglenids
| |
glycosome | carries out glycolysis | single-membrane compartment | Some Trypanosomes .
|
glyoxysome | conversion of fat into sugars | single-membrane compartment | plants |
hydrogenosome | energy & hydrogen production | double-membrane compartment | a few unicellular eukaryotes |
lysosome | breakdown of large molecules (e.g., proteins + polysaccharides) | single-membrane compartment | animals |
melanosome | pigment storage | single-membrane compartment | animals |
mitosome | probably plays a role in Iron–sulfur cluster (Fe–S) assembly | double-membrane compartment | a few unicellular eukaryotes that lack mitochondria |
myofibril | myocyte contraction |
bundled filaments | animals |
nucleolus | pre-ribosome production | protein–DNA–RNA | most eukaryotes |
ocelloid | detects light and possibly shapes, allowing phototaxis to take place | double-membrane compartment | members of the family Warnowiaceae |
parenthesome | not characterized | not characterized | fungi |
peroxisome | breakdown of metabolic hydrogen peroxide | single-membrane compartment | all eukaryotes |
porosome | secretory portal | single-membrane compartment | all eukaryotes |
proteasome | degradation of unneeded or damaged proteins by proteolysis | very large protein complex | all eukaryotes, all archaea, and some bacteria |
ribosome (80S) | translation of RNA into proteins |
RNA-protein | all eukaryotes |
stress granule | mRNA storage[22] | membraneless
( mRNP complexes)
|
most eukaryotes |
TIGER domain | mRNA encoding proteins | membraneless | most organisms |
vesicle |
material transport | single-membrane compartment | all eukaryotes |
Other related structures:
Prokaryotic organelles
However, there is increasing evidence of compartmentalization in at least some prokaryotes.[2] Recent research has revealed that at least some prokaryotes have microcompartments, such as carboxysomes. These subcellular compartments are 100–200 nm in diameter and are enclosed by a shell of proteins.[1] Even more striking is the description of membrane-bounded magnetosomes in bacteria, reported in 2006.[25][26]
The bacterial phylum
Compartmentalization is a feature of prokaryotic
Organelle/macromolecule | Main function | Structure | Organisms |
---|---|---|---|
anammoxosome |
anaerobic ammonium oxidation |
ladderane lipid membrane | "Candidatus" bacteria within Planctomycetota |
carboxysome | carbon fixation |
protein-shell bacterial microcompartment | some bacteria |
chlorosome | photosynthesis | light harvesting complex attached to cell membrane | green sulfur bacteria |
flagellum | movement in external medium | protein filament | some prokaryotes |
magnetosome | magnetic orientation | inorganic crystal, lipid membrane | magnetotactic bacteria |
nucleoid | DNA maintenance, transcription to RNA |
DNA-protein | prokaryotes |
pilus | Adhesion to other cells for conjugation or to a solid substrate to create motile forces. | a hair-like appendage sticking out (though partially embedded into) the plasma membrane | prokaryotic cells |
plasmid | DNA exchange | circular DNA | some bacteria |
ribosome (70S) | translation of RNA into proteins |
RNA-protein | bacteria and archaea |
thylakoid membranes | photosynthesis | photosystem proteins and pigments | mostly cyanobacteria |
See also
- CoRR hypothesis
- Ejectosome
- Endosymbiotic theory
- Organelle biogenesis
- Membrane vesicle trafficking
- Host–pathogen interaction
- Vesiculo-vacuolar organelle
References
- ^ S2CID 24561197.
- ^ PMID 20739411.
- ^ Peterson L (April 17, 2010). "Mastering the Parts of a Cell". Lesson Planet. Retrieved 2010-04-19.
- ^ Di Gregorio MA (2005). From Here to Eternity: Ernst Haeckel and Scientific Faith. Gottingen: Vandenhoeck & Ruprecht. p. 218.
- ^ Bütschli O (1888). Dr. H. G. Bronn's Klassen u. Ordnungen des Thier-Reichs wissenschaftlich dargestellt in Wort und Bild. Erster Band. Protozoa. Dritte Abtheilung: Infusoria und System der Radiolaria. p. 1412.
Die Vacuolen sind demnach in strengem Sinne keine beständigen Organe oder O r g a n u l a (wie Möbius die Organe der Einzelligen im Gegensatz zu denen der Vielzelligen zu nennen vorschlug).
- ^ Ryder JA, ed. (February 1889). "Embryology: The Structure of the Human Spermatozoon". American Naturalist. 23: 184.
It may possibly be of advantage to use the word organula here instead of organ, following a suggestion by Möbius. Functionally differentiated multicellular aggregates in multicellular forms or metazoa are in this sense organs, while, for functionally differentiated portions of unicellular organisms or for such differentiated portions of the unicellular germ-elements of metazoa, the diminutive organula is appropriate.
- ^ Robin C, Pouchet G, Duval MM, Retterrer E, Tourneux F (1891). Journal de l'anatomie et de la physiologie normales et pathologiques de l'homme et des animaux. F. Alcan.
- ^ a b
Möbius K (September 1884). "Das Sterben der einzelligen und der vielzelligen Tiere. Vergleichend betrachtet". Biologisches Centralblatt. 4 (13, 14): 389–392, 448.
Während die Fortpflanzungszellen der vielzelligen Tiere unthätig fortleben bis sie sich loslösen, wandern und entwickeln, treten die einzelligen Tiere auch durch die an der Fortpflanzung beteiligten Leibesmasse in Verkehr mit der Außenwelt und viele bilden sich dafür auch besondere Organula". Footnote on p. 448: "Die Organe der Heteroplastiden bestehen aus vereinigten Zellen. Da die Organe der Monoplastiden nur verschieden ausgebildete Teile e i n e r Zelle sind schlage ich vor, sie „Organula" zu nennen
- ^ Walker, Patrick (2009). Nuclear import of histone fold motif containing heterodimers by importin 13. Niedersächsische Staats-und Universitätsbibliothek Göttingen.
- ^ S2CID 11520942.
- ISBN 978-0-8053-6624-2.
- PMID 25747659.
- PMID 28225081.
- ISBN 978-0-397-52114-2.
- S2CID 42229928.
- S2CID 20393495.
- ISBN 978-0-306-47990-8.
- ISBN 978-0-8153-3218-3.
- PMID 6322306.
- ISBN 978-0815345244.
- PMID 16722803.
- PMID 18291657.
- PMID 17518518.
- PMID 3289587.
- S2CID 36909813.
- S2CID 4372846.
- ^ S2CID 21970703.
- S2CID 205694872. Retrieved 2020-08-03.
- PMID 15910279.
External links
- Media related to Organelles at Wikimedia Commons
- Tree of Life project: Eukaryotes
- Organelle Databases