The major membrane lipids
PtdCho - Phosphatidylcholine; PtdEtn - Phosphatidylethanolamine; PtdIns - Phosphatidylinositol; PtdSer - Phosphatidylserine.

The three major classes of membrane lipids are phospholipids, glycolipids, and cholesterol. Image File history File links Download high-resolution version (579x607, 10 KB) I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high-resolution version (579x607, 10 KB) I, the creator of this work, hereby release it into the public domain. ... Lecithin, also known as Phosphatidylcholine Lecithin is usually used as synonym for phosphatidylcholine, a phospholipid which is the major component of a phosphatide fraction which may be isolated from either egg yolk (in Greek lekithos - λεκιθος), or soy beans. ... Phosphatidylethanolamine is a lipid found in biological membranes. ... Chemical structure of sn-1-stearoyl-2-arachidonoyl phosphatidylinositol Phosphatidylinositol (abbreviated PtdIns, or PI) is a minor phospholipid component of eukaryotic cell membranes. ... Phosphatidylserine is a phospholipid nutrient found in fish, green leafy vegetables, soybeans and rice, and is essential for the normal functioning of neuronal cell membranes. ... Phospholipid Two schematic representations of a phospholipid. ... Glycolipids are carbohydrate-attached lipids. ... Cholesterol is a sterol (a combination steroid and alcohol) and a lipid found in the cell membranes of all body tissues, and transported in the blood plasma of all animals. ...

Phospholipids

Phospholipids and glycolipids consist of two long, nonpolar (hydrophobic) hydrocarbon chains linked to a hydrophilic head group.

In the phospholipids the head consist of phosphorylated either:

• Glycerol (and hence the name phosphoglycerides given to this group of lipids).
• Sphingosine (with only one member - sphingomyelin).

Sphingomyelin is a type of sphingolipid found in animal cell membranes, especially in the membranous myelin sheath which surrounds some nerve cell axons. ...

Glycolipids

In the glycolipids the head contains of sphingosine with one or several sugar units attached to it. The hydrophobic chains belong either to:

• two fatty acids - in the case of the phosphoglycerides.
• one FA and the hydrocarbon tail of sphingosine - in the case of sphingomyelin and the glycolipids.

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail (chain), which is either saturated or unsaturated. ... Sphingosine is a compound that forms a primary part of the sphingolipids, a class of cell membrane lipids which includes sphingomyelin, an important phospholipid. ...

Fatty acids

The FAs in phospho- and glycolipids usually contain an even number of carbon atoms, typically between 14 and 24. The 16- and 18-carbon FAs are the most common ones. FAs may be saturated or unsaturated, with the configuration of the double bonds nearly always cis. The length and the degree of unsaturation of FAs chains have a profound effect on membranes fluidity.

Phosphoglycerides

In phosphoglycerides, the hydroxyl groups at C-1 and C-2 of glycerol are esterified to the carboxyl groups of the FAs. The C-3 hydroxyl group is esterified to phosphoric acid. The resulting compound, called phosphatidate, is the simplest phosphoglycerate. Only small amounts of phosphatidate are present in membranes. However, it is a key intermediate in the biosynthesis of the other phosphoglycerides. Phosphatidate (red: phosphate group, blue & green: fatty acid) Phosphatidates are biochemical compounds that consist of a glycerol backbone, with a (usually) saturated fatty acid bonded to carbon-1, a (usually) unsaturated fatty acid bonded to carbon-2 and a phosphate group bonded to carbon-3. ...

Sphingosine

Sphingosine is an amino alcohol that contains long, unsaturates hydrocarbon chain. In sphingomyelin and glycolipids, the amino group of sphingosine is linked to a FAs by an amid bond. In sphingomyelin the primary hydroxyl group of sphingosine is esterified to phosphoryl choline. In glycolipids, the sugar component is attached to this group. The simplest glycolipid is cerebroside, in which there is only one sugar residue, either Glc or Gal. More complex glycolipids, such as gangliosides, contain a branched chain of as many as seven sugar residues. // Choline is a nutrient, essential for cardiovascular and brain function, and for cellular membrane composition and repair. ... Cerebrosides are glycosphingolipids which are important components in animal muscle and nerve cell membranes. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... Galactose (also called brain sugar) is a type of sugar found in dairy products, in sugar beets and other gums and mucilages. ... Ganglioside is a compound composed of a glycosphingolipid (ceramide and oligosaccharide) with one or more sialic acids (AKA n-acetylneuraminic acid) linked on the sugar chain. ...

See also

• Lipid bilayer

A diagonal molecular slab from the DPPC lipid bilayer simulation1; color scheme: PO4 - green, N(CH3)3 - violet, water - blue, terminal CH3 - yellow, O - red, glycol C - brown, chain C - grey. ...

External links

• MeSH Membrane+lipids