Cholesterol
<p ><b>Cholesterol</b>, from the <a href="http://en.wikipedia.org/wiki/Greek_language" title="Greek language" >Greek</a> <i>chole-</i> (<a href="http://en.wikipedia.org/wiki/Bile" title="Bile" >bile</a>) and <i>stereos</i> (solid) followed by the <a href="http://en.wikipedia.org/wiki/Chemical" title="Chemical" class="mw-redirect" >chemical</a> <a href="http://en.wikipedia.org/wiki/Suffix" title="Suffix" >suffix</a> <i>-ol</i> for an alcohol, is an <a href="http://en.wikipedia.org/wiki/Organic_compound" title="Organic compound" >organic </a><a href="http://en.wikipedia.org/wiki/Chemical_substance" title="Chemical substance" >chemical substance</a> classified as a waxy <a href="http://en.wikipedia.org/wiki/Steroid" title="Steroid" >steroid</a> of fat. It is an essential structural component of mammalian cell membranes and is required to establish proper <a href="http://en.wikipedia.org/wiki/Membrane_permeability" title="Membrane permeability" class="mw-redirect" >membrane permeability</a> and <a href="http://en.wikipedia.org/wiki/Membrane_fluidity" title="Membrane fluidity" >fluidity</a>.</p>
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In addition to its importance within cells, cholesterol is an important component in the hormonal systems of the body for the <a href="http://en.wikipedia.org/wiki/Biosynthesis" title="Biosynthesis" >manufacture</a> of <a href="http://en.wikipedia.org/wiki/Bile_acid" title="Bile acid" >bile acids</a>, <a href="http://en.wikipedia.org/wiki/Steroid_hormone" title="Steroid hormone" >steroid hormones</a>, and <a href="http://en.wikipedia.org/wiki/Vitamin_D" title="Vitamin D" >vitamin D</a>. Cholesterol is the principal <a href="http://en.wikipedia.org/wiki/Sterol" title="Sterol" >sterol</a> synthesized by animals; in <a href="http://en.wikipedia.org/wiki/Vertebrate" title="Vertebrate" >vertebrates</a> it is formed predominantly in the <a href="http://en.wikipedia.org/wiki/Liver" title="Liver" >liver</a>. </p>
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Small quantities are synthesized in other cellular organisms (<a href="http://en.wikipedia.org/wiki/Eukaryote" title="Eukaryote" >eukaryotes</a>) such as <a href="http://en.wikipedia.org/wiki/Plant" title="Plant" >plants</a> and<a href="http://en.wikipedia.org/wiki/Fungus" title="Fungus" >fungi</a>. It is almost completely absent among <a href="http://en.wikipedia.org/wiki/Prokaryote" title="Prokaryote" >prokaryotes</a> (i.e., bacteria).</p>
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Although cholesterol is important and necessary for human health, high levels of cholesterol in the blood have been linked to damage to arteries and <a href="http://en.wikipedia.org/wiki/Cardiovascular_disease" title="Cardiovascular disease" >cardiovascular disease</a>.<sup id="cite_ref-NHS:High_cholesterol_levels_1-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Cholesterol#cite_note-NHS:High_cholesterol_levels-1" >[2]</a></sup></p>
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<a href="http://en.wikipedia.org/wiki/Fran%C3%A7ois_Poulletier_de_la_Salle" title="François Poulletier de la Salle" >François Poulletier de la Salle</a> first identified cholesterol in solid form in <a href="http://en.wikipedia.org/wiki/Gallstone" title="Gallstone" >gallstones</a>, in 1769. However, it was only in 1815 that chemist <a href="http://en.wikipedia.org/wiki/Michel_Eug%C3%A8ne_Chevreul" title="Michel Eugène Chevreul" >Eugène Chevreul</a> named the compound "cholesterine".<sup id="cite_ref-pmid9478044_2-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Cholesterol#cite_note-pmid9478044-2" >[3]</a></sup></p>