Changes
From Opengenome.net
no edit summary
<p><strong>Polysaccharides</strong> (sometimes called <em><html><a title="Glycans" href="http://en.wikipedia.org/wiki/Glycans">glycans</a></html></em>) are relatively complex <html><a title="Carbohydrate" href="http://en.wikipedia.org/wiki/Carbohydrate">carbohydrates</a></html>.</p>
<p>They are <html><a title="Polymer" href="http://en.wikipedia.org/wiki/Polymer">polymers</a></html> made up of many <html><a title="Monosaccharide" href="http://en.wikipedia.org/wiki/Monosaccharide">monosaccharides</a></html> joined together by glycosidic linkages. They are therefore very large, often branched, molecules. They tend to be amorphous, insoluble in water, and have no sweet taste.</p>
<p>When all the constituent monosaccharides are of the same type they are termed <em>homopolysaccharides</em>; when more than one type of monosaccharide is present they are termed <em>heteropolysaccharides</em>.</p>
<p>Examples include storage polysaccharides such as <html><a title="Starch" href="http://en.wikipedia.org/wiki/Starch">starch</a></html> and <html><a title="Glycogen" href="http://en.wikipedia.org/wiki/Glycogen">glycogen</a></html> and structural polysaccharides such as <html><a title="Cellulose" href="http://en.wikipedia.org/wiki/Cellulose">cellulose</a></html> and <html><a title="Chitin" href="http://en.wikipedia.org/wiki/Chitin">chitin</a></html>.</p>
<p>Polysaccharides have a general formula of C<sub>n</sub>(H<sub>2</sub>O)<sub>n-1</sub> where n is usually a large number between 200 and 500.</p>
<table id="toc" summary="Contents" class="toc">
<tbody>
<tr>
<td>
<div id="toctitle">
<h2>Contents</h2>
<span class="toctoggle">[<html><a class="internal" id="togglelink" href="javascript:toggleToc()">hide</a></html>]</span></div>
<ul>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Starches"><span class="tocnumber">1</span> <span class="toctext">Starches</span></a> </li>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Glycogen"><span class="tocnumber">2</span> <span class="toctext">Glycogen</span></a> </li>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Cellulose"><span class="tocnumber">3</span> <span class="toctext">Cellulose</span></a> </li>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Acidic_polysaccharides"><span class="tocnumber">4</span> <span class="toctext">Acidic polysaccharides</span></a> </li>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Bacterial_Capsule_Polysaccharides"><span class="tocnumber">5</span> <span class="toctext">Bacterial Capsule Polysaccharides</span></a> </li>
</ul>
</td>
</tr>
</tbody>
</table>
<p>
<script type="text/javascript">
//<![CDATA[
if (window.showTocToggle) { var tocShowText = "show"; var tocHideText = "hide"; showTocToggle(); }
//]]>
</script>
</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=1">edit</a></html>]</div>
<p><html><a id="Starches" name="Starches"></a></html></p>
<h2>Starches</h2>
<p>Starches are glucose polymers in which glucopyranose units are bonded by <em>alpha-</em>linkages. <html><a title="Amylose" href="http://en.wikipedia.org/wiki/Amylose">Amylose</a></html> consists of a linear chain of several hundred glucose molecules. <html><a title="Amylopectin" href="http://en.wikipedia.org/wiki/Amylopectin">Amylopectin</a></html> is a branched molecule made of several thousand of glucose units.<br /><html><a title="Starch" href="http://en.wikipedia.org/wiki/Starch">Starches</a></html> are <html><a title="Insoluble" href="http://en.wikipedia.org/wiki/Insoluble">insoluble</a></html> in <html><a title="Water" href="http://en.wikipedia.org/wiki/Water">water</a></html>. They can be digested by hydrolysis catalyzed by enzymes called <html><a title="Amylase" href="http://en.wikipedia.org/wiki/Amylase">amylases</a></html>, which can break the <em>alpha-</em>linkages. Humans and other animals have amylases, so they can digest starches. <html><a title="Potato" href="http://en.wikipedia.org/wiki/Potato">Potato</a></html>, <html><a title="Rice" href="http://en.wikipedia.org/wiki/Rice">rice</a></html>, <html><a title="Wheat" href="http://en.wikipedia.org/wiki/Wheat">wheat</a></html>, and <html><a title="Maize" href="http://en.wikipedia.org/wiki/Maize">maize</a></html> are major sources of starch in the human diet.</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=2">edit</a></html>]</div>
<p><html><a id="Glycogen" name="Glycogen"></a></html></p>
<h2>Glycogen</h2>
<p><html><a title="Glycogen" href="http://en.wikipedia.org/wiki/Glycogen">Glycogen</a></html> is the storage form of glucose in <html><a title="Animal" href="http://en.wikipedia.org/wiki/Animal">animals</a></html>. It is a branched polymer of glucose. Glycogen can be broken down to form substrates for respiration, through the process of <html><a title="Glycogenolysis" href="http://en.wikipedia.org/wiki/Glycogenolysis">glycogenolysis</a></html>. This involves the breaking of most of the C-O-C bonds between the glucose molecules by the addition of a phosphate, rather than a water as in <html><a title="Hydrolysis" href="http://en.wikipedia.org/wiki/Hydrolysis">hydrolysis</a></html>. This process yields phosphorylated glucose molecules, which can be metabolized with a saving of one <html><a title="Adenosine triphosphate" href="http://en.wikipedia.org/wiki/Adenosine_triphosphate">ATP</a></html> molecule.</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=3">edit</a></html>]</div>
<p><html><a id="Cellulose" name="Cellulose"></a></html></p>
<h2>Cellulose</h2>
<p>The structural components of <html><a title="Plant" href="http://en.wikipedia.org/wiki/Plant">plants</a></html> are formed primarily from <html><a title="Cellulose" href="http://en.wikipedia.org/wiki/Cellulose">cellulose</a></html>. Wood is largely cellulose and <html><a title="Lignin" href="http://en.wikipedia.org/wiki/Lignin">lignin</a></html>, while <html><a title="Paper" href="http://en.wikipedia.org/wiki/Paper">paper</a></html> and <html><a title="Cotton" href="http://en.wikipedia.org/wiki/Cotton">cotton</a></html> are nearly pure cellulose. Cellulose is a <html><a title="Polymer" href="http://en.wikipedia.org/wiki/Polymer">polymer</a></html> made with repeated glucose units bonded together by <em>beta-</em>linkages. Humans and many other animals lack an enzyme to break the <em>beta-</em>linkages, so they do not digest cellulose. Certain animals can digest cellulose, because bacteria possessing the enzyme are present in their gut. The classic example is the <html><a title="Termite" href="http://en.wikipedia.org/wiki/Termite">termite</a></html>.</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=4">edit</a></html>]</div>
<p><html><a id="Acidic_polysaccharides" name="Acidic_polysaccharides"></a></html></p>
<h2>Acidic polysaccharides</h2>
<p>Acidic polysaccharides are polysaccharides that contain <html><a title="Carboxyl group" href="http://en.wikipedia.org/wiki/Carboxyl_group">carboxyl groups</a></html>, phosphate groups and/or <html><a class="new" title="Sulfuric ester group" href="http://en.wikipedia.org/w/index.php?title=Sulfuric_ester_group&action=edit">sulfuric ester groups</a></html>.</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=5">edit</a></html>]</div>
<p><html><a id="Bacterial_Capsule_Polysaccharides" name="Bacterial_Capsule_Polysaccharides"></a></html></p>
<h2>Bacterial Capsule Polysaccharides</h2>
<p>Pathogenic bacteria commonly produce a thick, mucous-like, layer of polysaccharide. This "capsule" cloaks antigenic proteins on the bacterial surface that would otherwise provoke an immune response and thereby lead to the destruction of the bacteria. Capsular polysaccharides are water soluble, commonly acidic, and have <html><a title="Molecular weight" href="http://en.wikipedia.org/wiki/Molecular_weight">molecular weights</a></html> on the order of 100-1000 <html><a title="Atomic mass unit" href="http://en.wikipedia.org/wiki/Atomic_mass_unit">kDa</a></html>. They are linear and consist of regularly repeating subunits of one ~ six monosaccharides. There is enormous structural diversity; nearly two hundred different polysaccharides are produced by <html><a title="Escherichia coli" href="http://en.wikipedia.org/wiki/Escherichia_coli">E. coli</a></html> alone. Mixtures of capsular polysaccharides, either <html><a title="Conjugate vaccine" href="http://en.wikipedia.org/wiki/Conjugate_vaccine">conjugated</a></html> or native are used as vaccines.</p>
<p>Bacteria and many other microbes, including fungi and algae, often secrete polysaccharides as an evolutionary adaptation to help them adhere to surfaces and to prevent them from drying out. Humans have developed some of these polysaccharides into useful products, including <html><a title="Xanthan gum" href="http://en.wikipedia.org/wiki/Xanthan_gum">xanthan gum</a></html>, <html><a title="Dextran" href="http://en.wikipedia.org/wiki/Dextran">dextran</a></html>, gellan gum, and <html><a title="Pullulan" href="http://en.wikipedia.org/wiki/Pullulan">pullulan</a></html>.</p>
<!-- Saved in parser cache with key enwiki:pcache:idhash:23978-0!1!0!0!!en!2 and timestamp 20060209020407 -->
<div class="printfooter">Retrieved from "<html><a href="http://en.wikipedia.org/wiki/Polysaccharide">http://en.wikipedia.org/wiki/Polysaccharide</a></html>"</div>
<p>They are <html><a title="Polymer" href="http://en.wikipedia.org/wiki/Polymer">polymers</a></html> made up of many <html><a title="Monosaccharide" href="http://en.wikipedia.org/wiki/Monosaccharide">monosaccharides</a></html> joined together by glycosidic linkages. They are therefore very large, often branched, molecules. They tend to be amorphous, insoluble in water, and have no sweet taste.</p>
<p>When all the constituent monosaccharides are of the same type they are termed <em>homopolysaccharides</em>; when more than one type of monosaccharide is present they are termed <em>heteropolysaccharides</em>.</p>
<p>Examples include storage polysaccharides such as <html><a title="Starch" href="http://en.wikipedia.org/wiki/Starch">starch</a></html> and <html><a title="Glycogen" href="http://en.wikipedia.org/wiki/Glycogen">glycogen</a></html> and structural polysaccharides such as <html><a title="Cellulose" href="http://en.wikipedia.org/wiki/Cellulose">cellulose</a></html> and <html><a title="Chitin" href="http://en.wikipedia.org/wiki/Chitin">chitin</a></html>.</p>
<p>Polysaccharides have a general formula of C<sub>n</sub>(H<sub>2</sub>O)<sub>n-1</sub> where n is usually a large number between 200 and 500.</p>
<table id="toc" summary="Contents" class="toc">
<tbody>
<tr>
<td>
<div id="toctitle">
<h2>Contents</h2>
<span class="toctoggle">[<html><a class="internal" id="togglelink" href="javascript:toggleToc()">hide</a></html>]</span></div>
<ul>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Starches"><span class="tocnumber">1</span> <span class="toctext">Starches</span></a> </li>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Glycogen"><span class="tocnumber">2</span> <span class="toctext">Glycogen</span></a> </li>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Cellulose"><span class="tocnumber">3</span> <span class="toctext">Cellulose</span></a> </li>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Acidic_polysaccharides"><span class="tocnumber">4</span> <span class="toctext">Acidic polysaccharides</span></a> </li>
<li class="toclevel-1"><a href="http://en.wikipedia.org/wiki/Polysaccharide#Bacterial_Capsule_Polysaccharides"><span class="tocnumber">5</span> <span class="toctext">Bacterial Capsule Polysaccharides</span></a> </li>
</ul>
</td>
</tr>
</tbody>
</table>
<p>
<script type="text/javascript">
//<![CDATA[
if (window.showTocToggle) { var tocShowText = "show"; var tocHideText = "hide"; showTocToggle(); }
//]]>
</script>
</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=1">edit</a></html>]</div>
<p><html><a id="Starches" name="Starches"></a></html></p>
<h2>Starches</h2>
<p>Starches are glucose polymers in which glucopyranose units are bonded by <em>alpha-</em>linkages. <html><a title="Amylose" href="http://en.wikipedia.org/wiki/Amylose">Amylose</a></html> consists of a linear chain of several hundred glucose molecules. <html><a title="Amylopectin" href="http://en.wikipedia.org/wiki/Amylopectin">Amylopectin</a></html> is a branched molecule made of several thousand of glucose units.<br /><html><a title="Starch" href="http://en.wikipedia.org/wiki/Starch">Starches</a></html> are <html><a title="Insoluble" href="http://en.wikipedia.org/wiki/Insoluble">insoluble</a></html> in <html><a title="Water" href="http://en.wikipedia.org/wiki/Water">water</a></html>. They can be digested by hydrolysis catalyzed by enzymes called <html><a title="Amylase" href="http://en.wikipedia.org/wiki/Amylase">amylases</a></html>, which can break the <em>alpha-</em>linkages. Humans and other animals have amylases, so they can digest starches. <html><a title="Potato" href="http://en.wikipedia.org/wiki/Potato">Potato</a></html>, <html><a title="Rice" href="http://en.wikipedia.org/wiki/Rice">rice</a></html>, <html><a title="Wheat" href="http://en.wikipedia.org/wiki/Wheat">wheat</a></html>, and <html><a title="Maize" href="http://en.wikipedia.org/wiki/Maize">maize</a></html> are major sources of starch in the human diet.</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=2">edit</a></html>]</div>
<p><html><a id="Glycogen" name="Glycogen"></a></html></p>
<h2>Glycogen</h2>
<p><html><a title="Glycogen" href="http://en.wikipedia.org/wiki/Glycogen">Glycogen</a></html> is the storage form of glucose in <html><a title="Animal" href="http://en.wikipedia.org/wiki/Animal">animals</a></html>. It is a branched polymer of glucose. Glycogen can be broken down to form substrates for respiration, through the process of <html><a title="Glycogenolysis" href="http://en.wikipedia.org/wiki/Glycogenolysis">glycogenolysis</a></html>. This involves the breaking of most of the C-O-C bonds between the glucose molecules by the addition of a phosphate, rather than a water as in <html><a title="Hydrolysis" href="http://en.wikipedia.org/wiki/Hydrolysis">hydrolysis</a></html>. This process yields phosphorylated glucose molecules, which can be metabolized with a saving of one <html><a title="Adenosine triphosphate" href="http://en.wikipedia.org/wiki/Adenosine_triphosphate">ATP</a></html> molecule.</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=3">edit</a></html>]</div>
<p><html><a id="Cellulose" name="Cellulose"></a></html></p>
<h2>Cellulose</h2>
<p>The structural components of <html><a title="Plant" href="http://en.wikipedia.org/wiki/Plant">plants</a></html> are formed primarily from <html><a title="Cellulose" href="http://en.wikipedia.org/wiki/Cellulose">cellulose</a></html>. Wood is largely cellulose and <html><a title="Lignin" href="http://en.wikipedia.org/wiki/Lignin">lignin</a></html>, while <html><a title="Paper" href="http://en.wikipedia.org/wiki/Paper">paper</a></html> and <html><a title="Cotton" href="http://en.wikipedia.org/wiki/Cotton">cotton</a></html> are nearly pure cellulose. Cellulose is a <html><a title="Polymer" href="http://en.wikipedia.org/wiki/Polymer">polymer</a></html> made with repeated glucose units bonded together by <em>beta-</em>linkages. Humans and many other animals lack an enzyme to break the <em>beta-</em>linkages, so they do not digest cellulose. Certain animals can digest cellulose, because bacteria possessing the enzyme are present in their gut. The classic example is the <html><a title="Termite" href="http://en.wikipedia.org/wiki/Termite">termite</a></html>.</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=4">edit</a></html>]</div>
<p><html><a id="Acidic_polysaccharides" name="Acidic_polysaccharides"></a></html></p>
<h2>Acidic polysaccharides</h2>
<p>Acidic polysaccharides are polysaccharides that contain <html><a title="Carboxyl group" href="http://en.wikipedia.org/wiki/Carboxyl_group">carboxyl groups</a></html>, phosphate groups and/or <html><a class="new" title="Sulfuric ester group" href="http://en.wikipedia.org/w/index.php?title=Sulfuric_ester_group&action=edit">sulfuric ester groups</a></html>.</p>
<div class="editsection" style="FLOAT: right; MARGIN-LEFT: 5px">[<html><a title="Polysaccharide" href="http://en.wikipedia.org/w/index.php?title=Polysaccharide&action=edit&section=5">edit</a></html>]</div>
<p><html><a id="Bacterial_Capsule_Polysaccharides" name="Bacterial_Capsule_Polysaccharides"></a></html></p>
<h2>Bacterial Capsule Polysaccharides</h2>
<p>Pathogenic bacteria commonly produce a thick, mucous-like, layer of polysaccharide. This "capsule" cloaks antigenic proteins on the bacterial surface that would otherwise provoke an immune response and thereby lead to the destruction of the bacteria. Capsular polysaccharides are water soluble, commonly acidic, and have <html><a title="Molecular weight" href="http://en.wikipedia.org/wiki/Molecular_weight">molecular weights</a></html> on the order of 100-1000 <html><a title="Atomic mass unit" href="http://en.wikipedia.org/wiki/Atomic_mass_unit">kDa</a></html>. They are linear and consist of regularly repeating subunits of one ~ six monosaccharides. There is enormous structural diversity; nearly two hundred different polysaccharides are produced by <html><a title="Escherichia coli" href="http://en.wikipedia.org/wiki/Escherichia_coli">E. coli</a></html> alone. Mixtures of capsular polysaccharides, either <html><a title="Conjugate vaccine" href="http://en.wikipedia.org/wiki/Conjugate_vaccine">conjugated</a></html> or native are used as vaccines.</p>
<p>Bacteria and many other microbes, including fungi and algae, often secrete polysaccharides as an evolutionary adaptation to help them adhere to surfaces and to prevent them from drying out. Humans have developed some of these polysaccharides into useful products, including <html><a title="Xanthan gum" href="http://en.wikipedia.org/wiki/Xanthan_gum">xanthan gum</a></html>, <html><a title="Dextran" href="http://en.wikipedia.org/wiki/Dextran">dextran</a></html>, gellan gum, and <html><a title="Pullulan" href="http://en.wikipedia.org/wiki/Pullulan">pullulan</a></html>.</p>
<!-- Saved in parser cache with key enwiki:pcache:idhash:23978-0!1!0!0!!en!2 and timestamp 20060209020407 -->
<div class="printfooter">Retrieved from "<html><a href="http://en.wikipedia.org/wiki/Polysaccharide">http://en.wikipedia.org/wiki/Polysaccharide</a></html>"</div>
