Glycerophospholipid
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[[Image:Glycerine chemical structure.png|thumb|[[Glycerol]]]]
[[Image:Phospholipid.svg|thumb|[[Phosphoglyceride]]]]
'''Glycerophospholipids''' or '''phosphoglycerides''' are [[glycerol]]-based [[phospholipid]]s. They are the main component of [[biological membrane]]s.
==Structures==
The term glycerophospholipid signifies any derivative of [[sn-glycero-3-phosphoric acid]] that contains at least one O-[[acyl]], or O-[[alkyl]] or O-alk-1'-[[enyl]] [[residue]] attached to the glycerol [[functional group|moiety]] and a [[chemical polarity|polar]] head made of a [[nitrogenous]] base, a glycerol, or an [[inositol]] unit.
It contains a glycerol core with [[fatty acids]]. They can be the same or different subunits of fatty acids.
* Carbon 1 (tail, apolar) contains a fatty acid, typically ''saturated''
* Carbon 2 (tail, apolar) contains a fatty acid, typically ''unsaturated'' and in the [[cis]] conformation, thus appearing "bent"
* Carbon 3 (head, polar) contains a [[phosphate group]] or an [[alcohol]] attached to a phosphate group
==Nomenclature and stereochemistry==
Glycerophospholipids generally use a "sn" notation which stands for [[Stereochemistry|stereochemical]] numbering. When the letters "sn" appear in the nomenclature, by convention the [[hydroxyl group]] of the second carbon of glycerol (sn-2) is on the left on a [[Fischer projection]]. The numbering follows the one of Fischer's projections, being sn-1 the carbon at the top and sn-3 the one at the bottom.
The advantage of this particular notation is that the spatial conformation (R or L) of the glycero-molecule is determined intuitively by the residues on the positions sn-1 and sn-3.
For example sn-glycero-3-[[phosphoric acid]] and sn-glycero-1-[[phosphoric acid]] are [[enantiomers]].
==Examples of glycerophospholipids==
{| class="wikitable"
| '''Name''' || '''Image''' || '''Head''' || '''Image''' || '''Charge'''
|-
| [[Phosphatidyl choline]] (lecithin) || [[Image:Phosphatidyl-Choline.svg|200px]] || [[choline]] || [[Image:Choline-skeletal.png|140px]] || neutral
|-
| [[Phosphatidyl ethanolamine]] (cephalin) || [[Image:Phosphatidyl-Ethanolamine.png|200px]] || [[ethanolamine]] || [[Image:Ethanolamine.png|140px]] || neutral
|-
| [[Phosphatidyl inositol]] || [[Image:Phosphatidyl-Inositol.png|200px]] || [[inositol]] || [[Image:Inositol chair.png|140px]] || negative
|-
| [[Phosphatidyl serine]] || [[Image:Phosphatidyl-Serine.png|200px]] || [[serine]] || [[Image:L-serine-skeletal.png|140px]] || negative
|-
| [[cardiolipin|Bisphosphatidyl glycerol]] (cardiolipin) || [[Image:Diphosphatidyl-Glycerol.png|200px]] || - || - || negative
|}
[[Lecithin]] and [[cephalin]] are more common than the others in most human membranes, but [[cardiolipin]] is quite common in the inner membranes of [[mitochondria]].
==Uses==
===Use in membranes===
One of a glycerophospholipid's functions is to serve as a structural component of [[cell membrane]]s. The cell membrane seen under the [[electron microscope]] consists of two identifiable layers, or "leaflets", each of which is made up of an ordered row of glycerophospholipid molecules. The composition of each layer can vary widely depending on the type of cell.
* For example, in human [[erythrocyte]]s the ''[[cytosolic]]'' side (the side facing the [[cytosol]]) of the [[plasma membrane]] consists mainly of [[phosphatidylethanolamine]], [[phosphatidylserine]], and phosphatidylinositol.
* By contrast, the ''exoplasmic'' side (the side on the exterior of the cell) consists mainly of [[phosphatidylcholine]] and [[sphingomyelin]], a type of [[sphingolipid]].
Each glycerophospholipid molecule consists of a small [[chemical polarity|polar]] head group and two long [[hydrophobic]] chains. In the cell membrane, the two layers of phospholipids are arranged as follows:
* the [[hydrophobic]] tails point to each other and form a fatty, hydrophobic center
* the [[Ionic compound|ionic]] head groups are placed at the inner and outer surfaces of the cell membrane
This is a stable structure because the ionic hydrophilic head groups interact with the aqueous media inside and outside the cell, whereas the hydrophobic tails maximize hydrophobic interactions with each other and are kept away from the [[aqueous]] environments. The overall result of this structure is to construct a fatty barrier between the cell's interior and its surroundings.
===Use in emulsification===
Glycerophospholipids can also act as an [[emulsifying agent]] to promote [[dispersal]] of one substance into another. This is sometimes used in [[candy]] making.
==External links==
* [http://faculty.uca.edu/~johnc/phospholipid.jpg Diagram at uca.edu]
* [http://www.ualr.edu/botany/phospholipid.jpg Diagram at ualr.edu]
==See also==
*[[Phospholipid]]
*[[Biological membrane]]
==External links==
* {{MeshName|Glycerophospholipids}}
{{Phospholipids}}
[[Category:Phospholipids]]
[[Category:Membrane biology]]
[[de:Phosphoglyceride]]
[[es:Fosfoglicérido]]
[[fr:Phosphoglycérolipide]]
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