AskDefine | Define phospholipid

Dictionary Definition

phospholipid n : any of various compounds composed of fatty acids and phosphoric acid and a nitrogenous base; an important constituent of membranes

User Contributed Dictionary



  1. any lipid, such as lecithin or cephalin, consisting of a diglyceride combined with a phosphate group and a simple organic molecule such as choline or ethanolamine; they are important constituents of biological membranes



Extensive Definition

Phospholipids are a class of lipids, and a major component of all biological membranes, along with glycolipids, 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 bilayers, 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 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 However, this model has now been superseded, as through the study of lipid polymorphism it is now known that the behaviour of lipids under physiological (and other) conditions is not simple.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


  1. J.M.Berg, J.L. Tymoczko, and L. Stryer, Biochemistry. 5th ed. 2002, New York: W.H. Freeman. xxxviii, 974, [976] (various pages)
phospholipid in Bulgarian: Фосфолипид
phospholipid in Catalan: Fosfolípid
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phospholipid in Danish: Fosfolipid
phospholipid in German: Phospholipide
phospholipid in Estonian: Fosfolipiidid
phospholipid in Spanish: Fosfolípido
phospholipid in French: Phosphoacylglycérol
phospholipid in Korean: 인지질
phospholipid in Croatian: Fosfolipidi
phospholipid in Indonesian: Fosfolipid
phospholipid in Icelandic: Fosfólípið
phospholipid in Italian: Fosfolipide
phospholipid in Hebrew: פוספוליפיד
phospholipid in Luxembourgish: Phospholipid
phospholipid in Lithuanian: Fosfolipidai
phospholipid in Macedonian: Фосфолипид
phospholipid in Dutch: Fosfolipide
phospholipid in Japanese: リン脂質
phospholipid in Polish: Fosfolipidy
phospholipid in Portuguese: Fosfolípido
phospholipid in Russian: Фосфолипиды
phospholipid in Slovenian: Fosfolipid
phospholipid in Finnish: Fosfolipidi
phospholipid in Swedish: Fosfolipid
phospholipid in Thai: ฟอสโฟลิพิด
phospholipid in Turkish: Fosfolipit
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