Editing Lipid (section)

===Fatty acyls===
{{Main|Fatty acid}}
[[File:Prostacyclin-2D-skeletal.png|thumb|[[Prostacyclin|I<sub>2</sub> – Prostacyclin]] (an example of a [[prostaglandin]], an eicosanoid fatty acid)]]
[[Image:Leukotriene B4.svg|right|thumb|[[Leukotriene B4|LTB<sub>4</sub>]] (an example of a [[leukotriene]], an eicosanoid fatty acid)]]

Fatty acyls, a generic term for describing fatty acids, their conjugates and derivatives, are a diverse group of molecules synthesized by chain-elongation of an [[acetyl-CoA]] primer with [[malonyl-CoA]] or [[methylmalonyl-CoA]] groups in a process called [[fatty acid synthesis]].<ref name="Vance_2002"/><ref name="Brown_2007"/> They are made of a [[hydrocarbon chain]] that terminates with a [[carboxylic acid]] group; this arrangement confers the molecule with a [[chemical polarity|polar]], [[hydrophilic]] end, and a nonpolar, [[hydrophobic]] end that is [[insoluble]] in water. The fatty acid structure is one of the most fundamental categories of biological lipids and is commonly used as a building-block of more structurally complex lipids. The carbon chain, typically between four and 24 carbons long,<ref name="Hunt_1995"/> may be saturated or [[unsaturated compound|unsaturated]], and may be attached to [[functional group]]s containing [[oxygen]], [[halogen]]s, [[nitrogen]], and [[sulfur]]. If a fatty acid contains a double bond, there is the possibility of either a ''cis'' or ''trans'' [[cis–trans isomerism|geometric isomerism]], which significantly affects the molecule's [[molecular configuration|configuration]]. ''Cis''-double bonds cause the fatty acid chain to bend, an effect that is compounded with more double bonds in the chain. Three double bonds in 18-carbon ''[[linolenic acid]]'', the most abundant fatty-acyl chains of plant ''thylakoid membranes'', render these membranes highly ''fluid'' despite environmental low-temperatures,<ref name="YashRoy_1987"/> and also makes linolenic acid give dominating sharp peaks in high resolution 13-C NMR spectra of chloroplasts. This in turn plays an important role in the structure and function of cell membranes.<ref name = "Devlin_1997" />{{rp|193–5}} Most naturally occurring fatty acids are of the ''cis'' configuration, although the ''trans'' form does exist in some natural and partially hydrogenated fats and oils.<ref name="Hunter_2006"/>

Examples of biologically important fatty acids include the [[eicosanoid]]s, derived primarily from [[arachidonic acid]] and [[eicosapentaenoic acid]], that include [[prostaglandin]]s, [[leukotriene]]s, and [[thromboxane]]s. [[Docosahexaenoic acid]] is also important in biological systems, particularly with respect to sight.<ref name="The Lipid Chronicles">{{cite web|title=A Long Lipid, a Long Name: Docosahexaenoic Acid|url=http://www.samuelfurse.com/2011/12/a-long-name-a-long-lipid-docosahexaenoic-acid/ | vauthors = Furse S |work=The Lipid Chronicles|date=2011-12-02}}</ref><ref>{{cite web|title=DHA for Optimal Brain and Visual Functioning|url=http://www.dhaomega3.org/Overview/DHA-for-Optimal-Brain-and-Visual-Functioning|publisher=DHA/EPA Omega-3 Institute}}</ref> Other major lipid classes in the fatty acid category are the fatty esters and fatty amides. Fatty esters include important biochemical intermediates such as [[wax ester]]s, fatty acid thioester [[coenzyme A]] derivatives, fatty acid thioester [[Acyl carrier protein|ACP]] derivatives and fatty acid carnitines. The fatty amides include [[N-acylethanolamine|N-acyl ethanolamines]], such as the [[cannabinoid]] neurotransmitter [[anandamide]].<ref name="Fezza_2008"/>