Difference between revisions of "Murein"

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murein
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'''Definition'''
  
(Science: protein) [[cross]] [[linked]] [[peptidoglycan]] [[complex]] from the [[inner]] [[cell wall]] of all [[eubacteria]]. Constitutes 50% of the [[cell]] [[wall]] in [[gram-negative]] and 10% in [[gram-positive]] [[organisms]] and comprises _(1-4) linked N acetyl glucosamine and N acetyl muramic [[acid]] extensively cross linked by [[peptides]].
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''noun''
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A [[crystal]] [[lattice]] [[structure]] in the [[cell wall]] of [[eubacteria]] formed by the [[linear]] [[chain]]s of two alternating [[amino]] [[sugars]] ([[N-acetylglucosamine]] and [[N-acetylmuramic acid]]) that are connected to one another by the [[crosslinking]] of short [[peptide chain]]s attached to [[N-acetylmuramic acid]].
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'''Supplement'''
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Murein serves a structural role in the [[cell wall]] of [[bacteria]], giving structural strength and [[rigidity]]. It also serves to [[counteract]] [[osmotic pressure]] of the [[cytoplasm]]. It is involved in [[binary fission]] during bacterial cell [[reproduction]]. The [[Archaea]] have a similar layer called [[pseudopeptidoglycan]].
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The alternating [[sugars]] in the [[linear]] chain are joined by a β-(1,4)-glycosidic bond. On every [[N-acetylmuramic acid]], a short [[amino acid]] [[chain]] (of 4 to 5 [[residues]]) is attached. Hence, cross-linking between [[amino acid]]s attached to the [[sugar]] chain, particularly to [[N-acetylmuramic acid]], a 3D structure that is strong and rigid results.
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The [[sequence]] of [[amino acid]] and the [[molecular]] [[structure]] vary within [[species]] of [[bacteria]]. Murein is substantially thicker in [[Gram-positive bacteria]] than in [[Gram-negative bacteria]].
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''Word origin:'' ''mur(amic acid) + –ein''.
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<br>''Synonym:'' [[mucopeptide]], [[peptidoglycan]].
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<br>''Compare:'' [[pseudopeptidoglycan]].
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<br>''See also:'' [[cell wall]].

Latest revision as of 12:50, 25 June 2008

Definition

noun

A crystal lattice structure in the cell wall of eubacteria formed by the linear chains of two alternating amino sugars (N-acetylglucosamine and N-acetylmuramic acid) that are connected to one another by the crosslinking of short peptide chains attached to N-acetylmuramic acid.


Supplement

Murein serves a structural role in the cell wall of bacteria, giving structural strength and rigidity. It also serves to counteract osmotic pressure of the cytoplasm. It is involved in binary fission during bacterial cell reproduction. The Archaea have a similar layer called pseudopeptidoglycan.

The alternating sugars in the linear chain are joined by a β-(1,4)-glycosidic bond. On every N-acetylmuramic acid, a short amino acid chain (of 4 to 5 residues) is attached. Hence, cross-linking between amino acids attached to the sugar chain, particularly to N-acetylmuramic acid, a 3D structure that is strong and rigid results.

The sequence of amino acid and the molecular structure vary within species of bacteria. Murein is substantially thicker in Gram-positive bacteria than in Gram-negative bacteria.

Word origin: mur(amic acid) + –ein.
Synonym: mucopeptide, peptidoglycan.
Compare: pseudopeptidoglycan.
See also: cell wall.