Editing Lipid (section)

===Glycerophospholipids===
{{Main|Glycerophospholipid}}
[[File:Phosphatidyl-ethanolamine.svg|thumb|300px|[[Phosphatidylethanolamine]]]]

Glycerophospholipids, usually referred to as [[phospholipid]]s (though [[sphingomyelin]]s are also classified as phospholipids), are ubiquitous in nature and are key components of the [[lipid bilayer]] of cells,<ref name="The Structure of a Membrane">{{cite news|title=The Structure of a Membrane|url=http://www.samuelfurse.com/2011/11/the-structure-of-a-membrane/|work=The Lipid Chronicles|access-date=2011-12-31|date=2011-11-05}}</ref> as well as being involved in [[metabolism]] and [[cell signaling]].<ref name="Berridge_1989"/> Neural tissue (including the brain) contains relatively high amounts of glycerophospholipids, and alterations in their composition has been implicated in various neurological disorders.<ref name="pmid10878232">{{cite journal | vauthors = Farooqui AA, Horrocks LA, Farooqui T | title = Glycerophospholipids in brain: their metabolism, incorporation into membranes, functions, and involvement in neurological disorders | journal = Chemistry and Physics of Lipids | volume = 106 | issue = 1 | pages = 1–29 | date = June 2000 | pmid = 10878232 | doi = 10.1016/S0009-3084(00)00128-6 }}</ref> Glycerophospholipids may be subdivided into distinct classes, based on the nature of the polar headgroup at the ''sn''-3 position of the glycerol backbone in [[eukaryote]]s and eubacteria, or the ''sn''-1 position in the case of [[archaebacteria]].<ref name="Ivanova_2007"/>

Examples of glycerophospholipids found in [[biological membrane]]s are [[phosphatidylcholine]] (also known as PC, GPCho or [[lecithin]]), [[phosphatidylethanolamine]] (PE or GPEtn) and [[phosphatidylserine]] (PS or GPSer). In addition to serving as a primary component of cellular membranes and binding sites for intra- and intercellular proteins, some glycerophospholipids in eukaryotic cells, such as [[phosphatidylinositol]]s and [[phosphatidic acid]]s are either precursors of or, themselves, membrane-derived [[second messenger system|second messengers]].<ref name = "van_Holde_1996" />{{rp|844}} Typically, one or both of these hydroxyl groups are acylated with long-chain fatty acids, but there are also alkyl-linked and 1Z-alkenyl-linked ([[plasmalogen]]) glycerophospholipids, as well as dialkylether variants in archaebacteria.<ref name="Paltauf_1994"/>