Peptidoglicano: Diferenzas entre revisións
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O '''peptidoglicano''', tamén chamado '''mureína''', é un [[polímero]] formado por [[carbohidrato|azucres]] e [[aminoácido]]s que forma unha capa reticular que rodea a [[membrana plasmática]] da maioría das [[bacteria]]s (pero non das [[arquea]]s) e que constitúe a súa [[parede celular]]. O compoñente carbohidrato do peptidoglicano é un hetero[[polisacárido]] formado por residuos alternantes dos [[monosacárido]]s [[N-acetilglicosamina|''N''-acetilglicosamina]] e [[ácido N-acetilmurámico|ácido ''N''-acetilmuráamico]], unidos entre si por [[enlace glicosídico]] β-(1,4). As cadeas deste heteropolisacárido dispóñense paralelamente. Unido ao ácido ''N''-acetilmurámico está o compoñente aminoacídico, que é un [[péptido]] de tres a cinco aminoácidos. Esta cadea peptídica pode establecer enlaces cruzados cos péptidos doutras cadeas do heteropolisacárido, formando unha capa reticular tridimensional. <ref>[http://pharmaxchange.info/press/2011/03/animation-of-synthesis-of-peptidoglycan-layer/ Animation of Synthesis of Peptidoglycan Layer]</ref>
Algunhas [[Archaea]] O The peptidoglycan layer is substantially thicker in [[Gram-positive]] [[bacteria]] (20 to 80 nanometers) than in [[Gram-negative]] bacteria (7 to 8 nanometers), with the attachment of the [[S-layer]]. Peptidoglycan forms around 90% of the [[dry weight]] of Gram-positive bacteria but only 10% of Gram-negative strains. Thus, presence of high levels of peptidoglycan is the primary determinant of the characterisation of bacteria as gram-positive.<ref>C.Michael Hogan. 2010. [http://www.eoearth.org/article/Bacteria?topic=49480 ''Bacteria''. Encyclopedia of Earth. eds. Sidney Draggan and C.J.Cleveland, National Council for Science and the Environment, Washington DC]</ref> In Gram-positive strains, it is important in attachment roles and stereotyping purposes.<ref name=Salton1996>{{cite book | author = Salton MRJ, Kim KS | title = Structure. ''In:'' Baron's Medical Microbiology ''(Barron S ''et al.'', eds.)| edition = 4th | publisher = Univ of Texas Medical Branch | year = 1996 | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.289#297 | isbn=0-9631172-1-1 }}</ref> For both Gram-positive and Gram-negative bacteria, particles of approximately 2 nm can pass through the peptidoglycan.<ref>{{cite journal | author=Demchick PH, Koch AL | title=The permeability of the wall fabric of Escherichia coli and Bacillus subtilis | journal=Journal of Bacteriology | date=1 February 1996| pages=768–73| volume=178 | issue=3 |url=http://jb.asm.org/cgi/reprint/178/3/768 | pmid=8550511 | pmc=177723 }}</ref>
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