Organelle

From Wikipedia, the free encyclopedia Organelle Organelle In cell biology, an organelle (pronunciation: /ɔː(r)gəˡnɛl/) is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid membrane. Thus, the original definition was limited to structures of unicellular organisms. It would take several years before organulum, or the later term organelle, became accepted and expanded in meaning to include subcellular structures in multicellular organisms. Books around 1900 from Valentin Häcker,[6] Edmund Wilson[7] and Oscar Hertwig[8] still referred to cellular organs. Later, both terms came to be used side by side: Bengt Lidforss wrote 1915 (in German) about "Organs or Organells".[9] Around 1920, the term organelle was used to describe propulsion structures ("motor organelle complex", i.e., flagella and their anchoring)[10] and other protist structures, such as ciliates.[11] Alfred Kühn wrote about centrioles as division organelles, although he stated that, for Vahlkampfias, the alternative ’organelle’ or ’product of structural build-up’ had not yet been decided, without explaining the difference between the alternatives.[12] In his 1953 textbook, Max Hartmann used the term for extracellular (pellicula, shells, cell walls) and intracellular skeletons of protists.[13] Later, the now-widely-used[14][15][16][17] definition of organelle emerged, after which only cellular structures with surrounding membrane had been considered organelles. However, the more original definition of subcellular functional unit in general still coexists. [18][19] In 1978, Albert Frey-Wyssling suggested that the term organelle should refer only to structures that convert energy, such as centrosomes, ribosomes, and nucleoli.[20][21] This new definition, however, did not win wide recognition. A typical animal cell. Within the cytoplasm, the major organelles and cellular structures include: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (6) Golgi apparatus (7) cytoskeleton (8) smooth endoplasmic reticulum (9) mitochondria (10) vacuole (11) cytosol (12) lysosome (13) centriole. The name organelle comes from the idea that these structures are to cells what an organ is to the body (hence the name organelle, the suffix -elle being a diminutive). Organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organelles, particularly in eukaryotic cells. Prokaryotes were once thought not to have organelles, but some examples have now been identified.[1] History and Terminology In biology, organs are defined as confined functional units within an organism. The analogy 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. Credited as the first[2][3][4] to use a diminutive of organ (i.e. little organ) for cellular structures was German zoologist Karl August Möbius (1884), who used the term "organula" [5] (plural form of organulum, the diminutive of latin organum). From the context, it is clear that he referred to reproduction related structures of protists. In a footnote, which was published as a correction in the next issue of the journal, he justified his suggestion to call organs of unicellular organisms "organella" since they are only differently formed parts of one cell, in contrast to multicellular organs of multicellular organisms. Examples While most cell biologists consider the term organelle to be synonymous with "cell compartment," other cell biologists choose to limit the term organelle to include only those that are DNA-containing, having originated from formerly-autonomous microscopic organisms acquired via endosymbiosis.[22][23][24] The most notable of these organelles having originated from endosymbiont bacteria are: • mitochondria (in almost all eukaryotes) • chloroplasts (in plants, algae and protists). Other organelles are also suggested to have endosymbiotic origins, (notably the flagellum - see evolution of flagella). Not all parts of the cell qualify as organelles, and the use of the term to refer to some structures is disputed. 1 From Wikipedia, the free encyclopedia These structures are large assemblies of macromolecules that carry out particular and specialized functions, but they lack membrane boundaries. Such cell structures, which are not formally organelles, include: • ribosome • cytoskeleton • flagellum • centriole and microtubule-organizing center (MTOC). Organelle reticulum trans-fac cave) far from rou doplasm reticulum mitochondrion energy production Eukaryotic organelles Eukaryotes are one of the most structurally complex cell type, and by definition are in part organized by smaller interior compartments, that are themselves enclosed by lipid membranes that resemble the outermost cell membrane. The larger organelles, such as the nucleus and vacuoles, are easily visible with the light microscope. They were among the first biological discoveries made after the invention of the microscope. Not all eukaryotic cells have every one of the organelles listed below. Exceptional organisms have cells which do not include some organelles that might otherwise be considered universal to eukaryotes (such as mitochondria).[25] 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. Major eukaryotic organelles Organelle chloroplast (plastid) Main function Structure Organisms photosynthesis double-mem- plants, brane protists compartment (rare kleptovacuole storage, homeostasis DNA maintenance, RNA transcription double-mem- most has some brane eukaryotes theorize compartment engulfed ancestra ryotic ce (endosym single-mem- eukaryotes brane compartment nucleus double-mem- all has bulk brane eukaryotes genome compartment Mitochondria and chloroplasts, which have doublemembranes and their own DNA, are believed to have originated from incompletely consumed or invading prokaryotic organisms, which were adopted as a part of the invaded cell. This idea is supported in the Endosymbiotic theory. Minor eukaryotic organelles and cell components Organelle/ Macromolecule acrosome Notes Main function helps spermatoza fuse with ovum Structure Organisms single-mem- many brane animals compartment double-mem- all eukaryotic brane cells compartment endoplasmic reticulum has some genes; autophagosome vesicle which theorized to be sequesters cytoengulfed by the plasmic material plastic ancestral euka- and organelles organisms) ryotic cell for degradation (endosymbiosis) centriole anchor for translation single-mem- all rough endocytoskeleton and folding of brane eukaryotes plasmic reticcilium is covered movement in or new proteins compartment ulum (rough endowith ribosomes, of external meplasmic retichas folds that dium; "critical developmental ulum), expresare flat sacs; sion of lipids smooth endo- signaling path[26] (smooth endoplasmic retic- way" . plasmic ulum has glycosome folds carries out reticulum) that are tubular glycolysis sorting and modification of proteins single-mem- all cis-face brane eukaryotes glyoxysome (convex) compartment nearest to rough endoplasmic conversion of fat into sugars Microtubule protein Microtubule protein animals animals, protists, few plants Golgi apparatus single-mem- Some protobrane zoa, such as compartment Trypanosomes. single-mem- plants brane compartment 2 From Wikipedia, the free encyclopedia Organelle prokaryotic internal structures. An early false turn was hydrogenosome energy & hydro- double-mem- a few unicelgen production brane lular the idea developed in the 1970s that bacteria might contain compartment eukaryotes membrane folds termed mesosomes, but these were later shown to be artifacts produced by the chemicals lysosome breakdown of single-mem- most used to prepare the cells for electron microscopy.[28] large molecules brane eukaryotes However, more recent research has revealed that at (e.g., proteins + compartment least some prokaryotes have microcompartments such polysaccharides) as carboxysomes. These subcellular compartments are melanosome pigment storage single-mem- animals 100 - 200 nm in diameter and are enclosed by a shell of brane proteins.[1] Even more striking is the description of compartment membrane-bound magnetosomes in bacteria,[29][30] as well mitosome not double-mem- a few unicel- as the nucleus-like structures of the Planctomycetes [31] characterized brane lular that are surrounded by lipid membranes. compartment eukaryotes myofibril nucleolus parenthesome peroxisome muscular contraction ribosome production not characterized bundled filaments animals Prokaryotic organelles and cell components Structure Organisms Organelle/ Main function Macromolecule carbon fixation protein-DNA- most carboxysome RNA eukaryotes not fungi characterized chlorosome protein-shell some bacteria compartment photosynthesis light harvest- green sulfur ing complex bacteria movement in external medium magnetic orientation DNA maintenance, transcription to RNA translation of RNA into proteins protein filament inorganic crystal, lipid membrane DNA-protein some prokaryotes and eukaryotes magnetotactic bacteria prokaryotes breakdown of single-mem- all flagellum metabolic hybrane eukaryotes drogen peroxide compartment translation of RNA into proteins material transport RNA-protein eukaryotes, magnetosome prokaryotes ribosome vesicle single-mem- all nucleoid brane eukaryotes compartment plasmid ribosome Other related structures: • cytosol • endomembrane system • nucleosome • microtubule • cell membrane DNA exchange circular DNA RNA-protein some bacteria eukaryotes, prokaryotes thylakoid photosynthesis photosystem mostly proteins and cyanobacteria pigments See also (A) Electron micrograph of Halothiobacillus neapolitanus cells, arrows highlight carboxysomes. (B) Image of intact carboxysomes isolated from H. neapolitanus. Scale bars are 100 nm.[27] • Cell • CoRR Hypothesis • Endosymbiotic theory Prokaryotic organelles Prokaryotes are not as structurally complex as eukaryotes, and were once thought not to have any internal structures enclosed by lipid membranes. In the past, they were often viewed as having little internal organization; but, slowly, details are emerging about References [1] ^ Kerfeld, Ca; Sawaya, Mr; Tanaka, S; Nguyen, Cv; Phillips, M; Beeby, M; Yeates, To (August 2005). "Protein structures forming the shell of primitive bacterial organelles.". Science (New York, N.Y.) 309 (5736): 936–8. doi:10.1126/science.1113397. PMID 16081736. 3 From Wikipedia, the free encyclopedia [2] 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.. pp. 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)." [3] Amer. Naturalist. 23, 1889, S. 183: „It may possibly be of advantage to use the word organula here instead of organ, following a suggestion by Möbius. Functionallydifferentiated 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.“ Cited after : Oxford English Dictionary online, entry for „organelle“. [4] ’Journal de l’anatomie et de la physiologie normales et pathologiques de l’homme et des animaux’ at Google Books [5] Möbius, K. (September 1884). "Das Sterben der einzelligen und der vielzelligen Tiere. Vergleichend betrachtet". Biologisches Centralblatt 4 (13,14): 389–392, 448. http://www.dietzellab.de/goodies/history/. "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". [6] Häcker, Valentin (1899). Zellen- und Befruchtungslehre. Jena: Verlag von Gustav Fisher. [7] Wilson, Edmund B. (1900). The cell in Development and Inheritance (second ed.). New York: The Macmillan Company. [8] Hertwig, Oscar (1906). Allgemeine Biologie. Zweite Auflage des Lehrbuchs „Die Zelle und die Gewebe“. Jena: Verlag von Gustav Fischer. [9] Lidforss, B. (1915). "Protoplasma". in Paul Hinneberg. Allgemeine Biologie. Leipzig, Berlin: Verlag von B.G.Teubner. pp. 227 (218–264). "Eine Neubildung dieser Organe oder Organellen findet wenigstens bei höheren Pflanzen nicht statt" [10] Kofoid CA, Swezy O (1919). "Flagellate Affinities of Trichonympha". Proc. Natl. Acad. Sci. U.S.A. 5 (1): 9–16. doi:10.1073/pnas.5.1.9. PMID 16576345. [11] Cl. Hamburger, Handwörterbuch der Naturw. Bd. V, .S. 435. Infusorien. cited after Petersen, Hans (1919). "Über den Begriff des Lebens und die Stufen der biologischen Begriffsbildung". Archiv für Entwicklungsmechanik der Organismen (now: Organelle [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] Development Genes and Evolution) 45 (3): 423–442. doi:10.1007/BF02554406. Kühn, Alfred (1920). "Untersuchungen zur kausalen Analyse der Zellteilung. I. Teil: Zur Morphologie und Physiologie der Kernteilung von Vahlkampfia bistadialis". Archiv für Entwicklungsmechanik der Organismen (now: Development Genes and Evolution) 46: 259–327. doi:10.1007/BF02554424. "die Alternative: Organell oder Produkt der Strukturbildung". Hartmann, Max (1953). Allgemeine Biologie (4. Aufl. ed.). Stuttgart: Gustav Fisher Verlag. Nultsch, Allgemeine Botanik, 11. Aufl. 2001, Thieme Verlag Wehner/Gehring, Zoologie, 23. Aufl. 1995, Thieme Verlag Alberts et al., Molecular Biology of the Cell, 4. ed. 2002, online via "NCBI-Bookshelf" Brock, Mikrobiologie, 2. korrigierter Nachdruck (2003), der 1. Aufl. von 2001 Strasburgers Lehrbuch der Botanik für Hochschulen, 35. Aufl. (2002), S. 42 Alliegro MC, Alliegro MA, Palazzo RE (June 2006). "Centrosome-associated RNA in surf clam oocytes". Proc. Nat. Acad. Sci. USA 103 (24): 9034–9038. doi:10.1073/ pnas.0602859103. PMID 16754862. Frey-Wyssling, A (1978). "Definition of the organell concept" (in German). Gegenbaurs morphologisches Jahrbuch 124 (3): 455–7. ISSN 0016-5840. PMID 689352. Albert Frey-Wyssling: Concerning the concept "Organelle". Experientia 34, 547 (1978). doi:10.1007/BF01935984 Keeling, Pj; Archibald, Jm (April 2008). "Organelle evolution: what’s in a name?". Current biology : CB 18 (8): R345–7. doi:10.1016/j.cub.2008.02.065. PMID 18430636. http://www.sciencedirect.com/ science?_ob=ArticleURL&_udi=B6VRT-4SB9SNVK&_user=5731894&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_vers Retrieved on 2008-08-07. Imanian B, Carpenter KJ, Keeling PJ (March 2007). "Mitochondrial genome of a tertiary endosymbiont retains genes for electron transport proteins.". The Journal of eukaryotic microbiology 54 (2): 146–53. doi:10.1111/j.1550-7408.2007.00245.x. PMID 17403155. http://www3.interscience.wiley.com/cgi-bin/fulltext/ 118000427/HTMLSTART. Mullins, Christopher (2004). "Theory of Organelle Biogenesis: A Historical Perspective". The Biogenesis of Cellular Organelles. Springer Science+Business Media, National Institutes of Health. 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PMC: 1872035. http://biology.plosjournals.org/perlserv/?request=getdocument&doi=10.1371/journal.pbio.0050144. [28] Ryter A (1988). "Contribution of new cryomethods to a better knowledge of bacterial anatomy". Ann. Inst. Pasteur Microbiol. 139 (1): 33–44. doi:10.1016/ 0769-2609(88)90095-6. PMID 3289587. [29] Komeili A, Li Z, Newman DK, Jensen GJ (2006). "Magnetosomes are cell membrane invaginations organized by the actin-like protein MamK". Science 311 (5758): 242–5. doi:10.1126/science.1123231. PMID 16373532. Organelle [30] Scheffel A, Gruska M, Faivre D, Linaroudis A, Plitzko JM, Schüler D (2006). "An acidic protein aligns magnetosomes along a filamentous structure in magnetotactic bacteria". Nature 440 (7080): 110–4. doi:10.1038/nature04382. PMID 16299495. [31] Fuerst JA (2005). "Intracellular compartmentation in planctomycetes". Annu. Rev. Microbiol. 59: 299–328. doi:10.1146/annurev.micro.59.030804.121258. PMID 15910279. Bibliography • Alberts, Bruce et al. (2003). Essential Cell Biology, 2nd ed., Garland Science, 2003, ISBN 081533480X. • Alberts, Bruce et al. (2002). The Molecular Biology of the Cell, 4th ed., Garland Science, 2002, ISBN 0-8153-3218-1. External links • Tree of Life Eukaryotes Retrieved from "http://en.wikipedia.org/wiki/Organelle" Categories: Organelles, Cell anatomy This page was last modified on 14 May 2009, at 14:58 (UTC). All text is available under the terms of the GNU Free Documentation License. (See Copyrights for details.) Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a U.S. registered 501(c)(3) tax-deductible nonprofit charity. Privacy policy About Wikipedia Disclaimers 5