Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 8 : Lipids- Introduction, Classification and Functions

Sphingolipids

1. Second most important membrane constituent.
2. Very abundant in mammalian CNS.
3. Backbone is sphingosine (unbranched 18 carbon alcohol with 1 trans C=C between C-4 and C-5), NH3+ group at C-2, hydroxyl groups at C-1 and C-3.
4. Ceramides are intermediates of sphingolipid synthesis.
5. There are three families of sphingolipids:
• sphingomyelin - phosphocholine attached to C-1 hydroxyl group of ceramide; present in the myelin sheaths around some peripheral nerves.
• cerebrosides - glycosphingolipid; has 1 monosaccharide (galactose) attached by b-glycosidic linkage to C-1 of ceramide; most common is galactocerebroside, which is abundant in nervous tissue.
• gangliosides - glycosphingolipid containing N-acetylneuraminic acid; present on all cell surfaces.