Sterol
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2008-06-09T07:34:32Z
Littlealien182
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Added {{[[Template:expand|expand]]}} tag to article. using [[WP:FRIENDLY|Friendly]]
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[[Image:Sterol skeleton.png|right]]
'''Sterols''', or '''steroid alcohols''' are a subgroup of [[steroid]]s with a [[hydroxyl group]] at the 3-position of the A-ring.<ref>{{cite journal |author=Fahy E, Subramaniam S, Brown HA, ''et al'' |title=A comprehensive classification system for lipids |journal=J. Lipid Res. |volume=46 |issue=5 |pages=839–61 |year=2005 |pmid=15722563 |url=http://www.jlr.org/cgi/content/full/46/5/839 |doi=10.1194/jlr.E400004-JLR200}}</ref> They are [[amphipathic lipids]] synthesized from [[acetyl-coenzyme A]] via the [[HMG-CoA reductase]] pathway. The overall molecule is quite flat. The hydroxyl group on the A ring is [[Chemical polarity|polar]]. The rest of the [[aliphatic]] chain is [[Chemical polarity|non-polar]].
Sterols of [[plant]]s are called ''[[phytosterol]]s'' and sterols of [[animal]]s are called ''zoosterols''. Important zoosterols are [[cholesterol]] and some [[steroid hormone]]s; notable phytosterols include [[campesterol]], [[sitosterol]], and [[stigmasterol]]. [[Ergosterol]] is a sterol present in the [[cell membrane]] of [[Fungus|fungi]], where it serves a role similar to cholesterol in animal cells.
Sterols and related compounds play essential roles in the physiology of [[eukaryote|eukaryotic]] organisms. For example, cholesterol forms part of the cellular membrane in animals, where it affects the cell membrane's fluidity and serves as [[secondary messenger]] in developmental signaling. In humans and other animals, [[corticosteroids]], such as [[cortisol]] act as signalling compounds in cellular communication and general metabolism.
Phytosterols may block cholesterol absorption sites in the human intestine thus helping to reduce cholesterol in humans. {{Fact|date=June 2008}}
==See also==
*[[Cholesterol]]
*[[Phytosterol]]
*[[Ergosterol]]
== References==
{{reflist}}
Molecular Biology of the Cell (Alberts et al., 2002) [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=cholesterol,bilayer&rid=mboc4.section.1864#1874]
== External links==
*[http://www.cyberlipid.org/sterols/ster0003.htm Sterols] Cyberlipid.org
{{Membrane lipids}}
{{Sterols}}
[[Category:Sterols]]
[[Category:Steroids]]
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