General Index


Amphipathic Lipids: Glycolipids

In glycolipids, the polar portion is a mono- or oligosaccharide bound by a b-glycosidic bond to an alcohol that most often is Sphingosine. Let's see the structure of a typical glycolipid, a Cerebroside:


In this structure we first see the Sphingosine:

In most cases the aminoalcohol of glycolipids is sphingosine. The different glycolipids differ in the oligosaccharide linked to the sphingosine.

The oligosaccharides show some regularities that allow them to be calssified into series. The table below show some of these series. All of them have a ceramide as hydrophobic portion.

Glycolipids

Series Sequence

Gal b(1,4)Gal b(1,1)-Cer

GalNAc b(1,3)-Gal a(1,4)-Gal b(1,4)-Glc b(1,1)-Cer

Gal b(1,3)-GalNAc b(1,4)-Gal b(1,4)-Glc b(1,1)-Cer

Gal b(1,3)-GlcNAc b(1,3)-Gal b(1,4)-Glc b(1,1)-Cer

Gal b(1,4)-GlcNac b(1,3)-Gal b(1,4)-Glc b(1,1)-Cer


An interesting group of glycolipids are the Gangliosides. In general, gangliosides are glycolipids of the ganglio- series in which the galactose in position 2 is substituted by one or more residues of Sialic Acid or N-Acetyl Neuraminic acid (NANA). There are many structural variants of gangliosides.

The structure of a ganglioside is as follows:


First we see the ceramide:

Note the great volume of the polar portion of these lipids. The gangliosides appear if the external leaflet of the membranes of many tissues, mainly in the Nervous Tissue, where they have an important function in the transmission of nerve impulse.


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