Lysosome: Difference between revisions
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[[File:Illu cell structure.jpg|thumb|350px|Various [[organelles]] labeled. The '''lysosome''' is labeled in the upper left.]] |
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[[image:biological cell.svg|thumb|350px|Schematic of typical animal cell, showing subcellular components. [[Organelle]]s:<br/> |
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(1) [[nucleolus]]<br/> |
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(2) [[cell nucleus|nucleus]]<br/> |
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(3) [[ribosomes]] (little dots)<br/> |
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(4) [[vesicle (biology)|vesicle]]<br/> |
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(5) rough [[endoplasmic reticulum]] (ER)<br/> |
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(6) [[Golgi apparatus]]<br/> |
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(7) [[Cytoskeleton]]<br/> |
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(8) smooth [[endoplasmic reticulum]]<br/> |
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(9) [[mitochondrion|mitochondria]]<br/> |
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(10) [[vacuole]]<br/> |
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(11) [[cytosol]]<br/> |
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(12) lysosome<br/> |
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(13) [[centriole]]s within [[centrosome]]]] |
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'''Lysosomes''' are cellular [[organelle]]s that contain acid [[hydrolase]] enzymes to break up waste materials and cellular debris. They are found in animal cells, while in yeast and plants the same roles are performed by lytic [[vacuole]]s.<ref>{{cite journal |author=Samaj J, Read ND, Volkmann D, Menzel D, Baluska F |title=The endocytic network in plants |journal=Trends Cell Biol. |volume=15 |issue=8 |pages=425–33 |year=2005 |month=August |pmid=16006126 |doi=10.1016/j.tcb.2005.06.006}}</ref> Lysosomes digest excess or worn-out [[organelle]]s, food particles, and engulfed [[virus]]es or [[bacteria]]. The [[biological membrane|membrane]] around a lysosome allows the [[digestive enzyme]]s to work at the 4.5 [[pH]] they require. Lysosomes fuse with [[vacuole]]s and dispense their enzymes into the [[vacuole]]s, digesting their contents. They are created by the addition of hydrolytic enzymes to early endosomes from the [[Golgi apparatus]]. The name ''lysosome'' derives from the Greek words '''[[lysis]]''', ''to separate'', and '''soma''', ''body''. They are frequently nicknamed "suicide-bags" or "suicide-sacs" by cell biologists due to their role in [[autolysis]]. Lysosomes were discovered by the Belgian cytologist [[Christian de Duve]] in the 1950s. |
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The size of lysosomes varies from 0.1–1.2 [[micrometre|μm]].<ref>{{cite book | last=Kuehnel | first=W | title=Color Atlas of Cytology, Histology, & Microscopic Anatomy | publisher=Thieme | year=2003 | edition=4th | pages=34 | isbn=1-58890-175-0 }}</ref> At [[pH]] 4.8, the interior of the lysosomes is acidic compared to the slightly alkaline [[cytosol]] (pH 7.2). The lysosome maintains this pH differential by pumping [[proton]]s (H<sup>+</sup> ions) from the cytosol across the [[Cell membrane|membrane]] via [[proton pump]]s and chloride [[ion channel]]s. The lysosomal membrane protects the cytosol, and therefore the rest of the [[cell (biology)|cell]], from the [[degradative enzyme]]s within the lysosome. The cell is additionally protected from any lysosomal acid [[hydrolases]] that leak into the cytosol, as these enzymes are pH-sensitive and do not function as well in the alkaline environment of the cytosol. |
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==Enzymes== |
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Some important enzymes found within lysosomes include: |
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*[[Lipase]], which digests [[lipid]]s |
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*[[Amylase]], which digests [[amylose]], [[starch]], and [[maltodextrins]] |
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*[[Protease]]s, which digest [[protein]]s |
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*[[Nuclease]]s, which digest [[nucleic acid]]s |
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*[[phosphoric acid]] monoesters. |
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Lysosomal enzymes are synthesized in the cytosol and the [[endoplasmic reticulum]], where they receive a [[mannose|mannose-6-phosphate]] tag that targets them for the lysosome {{Citation needed|date=April 2009}} . Aberrant lysosomal targeting causes [[inclusion-cell disease]], whereby enzymes do not properly reach the lysosome, resulting in accumulation of waste within these organelles.{{Citation needed|date=April 2009}} |
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==Functions== |
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Lysosomes are the cell's waste disposal system and can break up anything. They digest almost everything. They are used for the digestion of [[macromolecule]]s from [[phagocytosis]] (ingestion of other dying cells or larger extracellular material, like foreign invading microbes), [[endocytosis]] (where [[Receptor (biochemistry)|receptor protein]]s are recycled from the cell surface), and [[autophagy]] (where in old or unneeded organelles or proteins, or microbes that have invaded the cytoplasm are delivered to the lysosome). Autophagy may also lead to [[autophagy|autophagic cell death]], a form of [[programmed cell death|programmed self-destruction]], or [[autolysis]], of the cell, which means that the cell is digesting itself. |
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Other functions include digesting foreign bacteria (or other forms of waste) that invade a cell and helping repair damage to the [[plasma membrane]] by serving as a membrane patch, sealing the wound. In the past, lysosomes were thought to kill cells that are no longer wanted, such as those in the tails of [[tadpole]]s or in the web from the fingers of a 3- to 6-month-old [[fetus]]. While lysosomes digest some materials in this process, it is actually accomplished through programmed cell death, called [[apoptosis]].<ref>[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/Lysosomes.html Lysosomes and Peroxisomes<!-- Bot generated title -->]</ref><ref>Mader, Sylvia. (2007). Biology 9th ed. McGraw Hill. New York. ISBN 978-0072464634</ref> |
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==Clinical relevance== |
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There are a number of '''[[lysosomal storage diseases]]''' that are caused by the malfunction of the lysosomes or one of their digestive proteins; examples include [[Tay-Sachs disease]] and [[Pompe's disease]]. These diseases are caused by a defective or missing digestive protein, which leads to the accumulation of substrates within the cell, impairing [[metabolism]]. |
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In the broad sense, these can be classified as [[mucopolysaccharidosis|mucopolysaccharidoses]], [[GM2 gangliosidosis|GM<sub>2</sub> gangliosidoses]], [[lipid storage disorder]]s, [[glycoproteinosis|glycoproteinoses]], [[mucolipidosis|mucolipidoses]], or [[leukodystrophy|leukodystrophies]]. |
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<gallery> |
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File:Localisations02eng.jpg|Proteins in different [[cellular compartment]]s and structures tagged with [[green fluorescent protein]]. |
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</gallery> |
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==External links== |
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* [http://opm.phar.umich.edu/localization.php?localization=Lysosome%20membrane 3D structures of proteins associated with lysosome membrane] |
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* [http://www.hideandseek.org Hide and Seek Foundation For Lysosomal Research Team] |
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* [http://www.nytimes.com/2009/10/06/science/06cell.html Self-Destructive Behavior in Cells May Hold Key to a Longer Life] |
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* [http://content.nejm.org/cgi/content/full/NEJMoa0902630 Mutations in the Lysosomal Enzyme–Targeting Pathway and Persistent Stuttering] |
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==References== |
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<references /> |
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* {{NCBI-scienceprimer}} |
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{{organelles}} |
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[[Category:Organelles]] |
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[[af:Lisosoom]] |
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[[ar:يحلول]] |
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[[az:Lizosomlar]] |
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[[bg:Лизозома]] |
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[[ca:Lisosoma]] |
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[[cs:Lyzozom]] |
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[[da:Lysosom]] |
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[[de:Lysosom]] |
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[[et:Lüsosoom]] |
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[[el:Λυσόσωμα]] |
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[[es:Lisosoma]] |
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[[eo:Lizosomo]] |
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[[eu:Lisosoma]] |
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[[fa:کافندهتن]] |
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[[fr:Lysosome]] |
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[[gv:Leesosoom]] |
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[[gl:Lisosoma]] |
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[[ko:리소좀]] |
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[[hi:लाइसोसोम]] |
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[[hr:Lizosom]] |
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[[id:Lisosom]] |
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[[it:Lisosoma]] |
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[[he:ליזוזום]] |
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[[jv:Lisosom]] |
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[[ka:ლიზოსომა]] |
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[[la:Lysosoma]] |
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[[lv:Lizosoma]] |
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[[lb:Lysosom]] |
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[[lt:Lizosomos]] |
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[[hu:Lizoszóma]] |
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[[mk:Лизозом]] |
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[[nl:Lysosoom]] |
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[[ja:リソソーム]] |
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[[no:Lysosom]] |
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[[oc:Lisosòma]] |
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[[pl:Lizosom]] |
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[[pt:Lisossomo]] |
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[[ro:Lizozom]] |
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[[ru:Лизосома]] |
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[[simple:Lysosome]] |
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[[sk:Lyzozóm]] |
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[[sl:Lizosom]] |
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[[sr:Лизозом]] |
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[[sh:Lizozom]] |
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[[su:Lisosom]] |
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[[fi:Lysosomi]] |
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[[sv:Lysosom]] |
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[[th:ไลโซโซม]] |
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[[tr:Lizozom]] |
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[[uk:Лізосома]] |
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[[vi:Lysosome]] |
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[[zh:溶體]] |
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