Phospholipid 24505 221760022 2008-06-25T23:44:12Z SmackBot 433328 Date the maintenance tags or general fixes {{Expand|date=June 2008}} [[Image:Phospholipid.svg|thumb|185px|Phospholipid]] [[Image:phospholipid_structure.png|thumb|185px|Twoad group of the molecule, highlighted in red.<BR>The '''U''' indicates the uncharged hydrophobic portion of the molecule, highlighted in blue.]] [[Image:Phosphatidyl-Choline.svg|thumb|185px|[[Phosphatidyl choline]] is the major component of [[lecithin]]. It is also a source for [[choline]] in the synthesis of acetylcholine in cholinergic neurons.]] '''Phospholipids''' are a class of [[lipids]], and a major component of all [[biological membrane]]s, along with [[glycolipid]]s, [[cholesterol]] and [[proteins]]. Understanding of the aggregation properties of these molecules is known as [[lipid polymorphism]] and forms part of current academic research. ==Amphipathic character== Due to its polar nature, the head of a phospholipid is [[hydrophilic]] (attracted to [[water]]); the [[lipophilic]] (or often known as hydrophobic) tails are not attracted to water. When placed in water, phospholipids form one of a number of [[lipid phases]]. In biological systems this is restricted to [[bilayer]]s, in which the lipophilic tails line up against one another, forming a membrane with hydrophilic heads on both sides facing the water. This allows it to form [[liposomes]] spontaneously, or small lipid [[vesicle (biology)|vesicles]], which can then be used to transport materials into living organisms and study diffusion rates into or out of a cell membrane. This membrane is partially permeable, capable of elastic movement, and has [[fluid]] properties, in which embedded proteins (integral or peripheral proteins) and phospholipid molecules are able to move laterally. Such movement can be described by the [[Fluid Mosaic Model]], that describes the membrane as a mosaic of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane. [[Cholesterol]] contributes to membrane fluidity by hindering the packing together of phospholipids. However, this model has now been superseded, as through the study of [[lipid polymorphism]] it is now known that the behaviour of lipids under physiological (and other) conditions is not simple. == See also == *[[Alkylphosphocholines]] * [[Antiphospholipid syndrome]] * [[Biochemistry]] * [[Lipid]] * [[Lipid bilayer]] (e.g., [[Cell membrane]]) * [[Polymorphism (biophysics)]] ==References== # J.M.Berg, J.L. Tymoczko, and L. Stryer, ''Biochemistry''. 5th ed. 2002, New York: W.H. Freeman. xxxviii, 974, [976] (various pages) {{Membrane lipids}} {{Phospholipids}} [[Category:Phospholipids|*]] [[bg:Фосфолипид]] [[ca:Fosfolípid]] [[cs:Fosfolipid]] [[da:Fosfolipid]] [[de:Phospholipide]] [[et:Fosfolipiidid]] [[es:Fosfolípido]] [[fr:Phosphoacylglycérol]] [[ko:인지질]] [[hr:Fosfolipidi]] [[id:Fosfolipid]] [[is:Fosfólípið]] [[it:Fosfolipide]] [[he:פוספוליפיד]] [[lb:Phospholipid]] [[lt:Fosfolipidai]] [[mk:Фосфолипид]] [[nl:Fosfolipide]] [[ja:リン脂質]] [[pl:Fosfolipidy]] [[pt:Fosfolípido]] [[ru:Фосфолипиды]] [[sl:Fosfolipid]] [[fi:Fosfolipidi]] [[sv:Fosfolipid]] [[th:ฟอสโฟลิพิด]] [[tr:Fosfolipit]]