Glycolipids are lipids that contain a carbohydrate and a lipid component. The document discusses four main types of glycolipids: cerebrosides, gangliosides, sulfolipids, and sulfatides. Cerebrosides are found in high amounts in brain and nerve tissue. They contain sphingosine, a fatty acid, and usually galactose. Gangliosides contain additional sugars and sialic acids attached to a ceramide and are mainly found in brain tissue. Sulfolipids contain a sulfonic acid group in their hexose portion and are found in various tissues. Sulfatides are sulfated cerebrosides abundant in white brain matter. Glycolipids play important

1. STRUCTURE AND FUNCTIONS
OF GLYCOLIPIDS
- DAYANA.K

6. 1. Cerebrosides (Glycospingosides)
Occurrence
 Cerebrosides occur in large amounts in the white matter of brain
and in myelin sheath of nerve.
 They are not found in embryonic brain but develops as
medullation progress.
 In smaller amount they appear to be widely distributed in animal
tissues.
 In medullated nerves the concentration of cerebrosides are much
higher than in non-medullated nerve fibres.

7. Structure of cerebrosides
 The structure of cerebrosides contain a high molecular weight fatty acid,
sphingosine, sugar usually galactose but sometimes glucose is attached.
 But it has no glycerol, no phosphoric acid and no nitrogeneous base. They have
electric charge since their polar head groups are neutral.

8. Ceramide
 The name ceramide is commonly used to designate the sphingosine and fatty
acid(or N-acylsphingosine) portion of the cerebrosides.
 Here the sphingosine carries the galactose by glycosidic linkage on primary
group and the fatty acid by an amide linkage.
Psychosin
 By prolonged hydrolysis of any cerebroside with Ba(OH)2, FA is removed and it
yields psychosin (sphingosine+ sugar).
 Psychosin can be further hydrolysed to yield sphingosine and galactose.

9. Types of cerebrosides
 Individual cerebrosides are differentiated on the basis of fatty acid component.
Four types of cerebrosides have been isolated.
(a) Kerasin- contains saturated C24 lignoceric acid.
(b)phrenosin(cerebron)- contain 2-hydroxyl derivative of lignoceric acid
called cerebronic acid.
(c)Nervon- contains an unsaturated homologue of lignoceric acid called
nervonic acid.
(d)Oxynervon- contains a 2-hydroxyl derivative nervonic acid called
acid.

10. Clinical aspect of cerebrosides
Gaucher’s Disease
 An inherited disorder of cerebrosides metabolism (lipidosis).
 Inheritance: It is autosomal recessive
 Enzyme defect: Deficiency of the enzyme beta gluco-
cerebrosidase.
 In absence of the enzyme the cerebroside cannot be degraded
in the body as a result large amount of glucocerebroside
accumulate in liver, spleen, bone marrow and brain.

12. 2. Gangliosides
Occurrence
 In 1955, Klenk isolated a new type of glycolipid from brain tissue and named it as
ganglioside.
 These are found in ganglion cell of nervous tissue and in parenchymatous tissues
like spleen and erythrocytes.
 They make up about 6% of membrane lipids in the grey matter of the brain.
 They are also found in lesser amounts in membrane of non neural tissue.
 Gangliosides acts as receptor for toxic reagents like pathogens Vibrio cholera
influenza virus and tetanus toxin.
 It play a role in cell-cell interaction.

13. Structure of gangliosides
 The structure of ganglioside contain a ceramide (N-acylsphingosine) linked to 2
additional mole of carbohydrate, 1 mole of N-acetylgalactosamine and 1 to 5 mole
of N-acetylneuraminic acid (NANA).
Types of gangliosides:
 More than 15 different gangliosides have been determined. These are abbreviated
by the letter G with subscript M, D or T to designate they contain one, two or
sialic acid and NANA residues and a number or letter to distinguish different
members of a group from one another.
 In essence they consist of oligosaccharide chain attached to ceramide(N-
acylsphingosine by a sugar residue usually glucose. They lack phosphoric acid.
 Four important types are: GM-1, GM-2, GM-3 and GD-3.

15. Clinical aspect of Gangliosides
Tay-sachs Disease
 Inheritance: Autosomal recessive
 Enzyme defect: N-acetylgalactosaminidase
 Accumulation of gangliosides in brain and nervous system.
 The symptoms are mental retardation, difficulty in eating, Cherry
red spot in retina and blindness.

16. 3. Sulfolipids
Occurrence
 Lipid material containing sulphur present in various tissue found in
liver, kidney, testes, brain and certain tumours.
 Most abundant in white matter of brain. Several types of sulphur
containing lipids have been isolated from brain and other tissues.
 This glycolipid is widely distributed in plants. It is localized in
chloroplast and also found in chromatophores of photosynthetic
bacteria.

17. Structure of sulfolipids
 The sulfur in this compound present as a sulfonic group in a hexose
molecule, this may be included under a class of compound called
sulfolipids.

18. 4. Sulfatides
 A sulfate ester analogue of phrenosin. It is abundant in white matter
of brain.
 It is another sulphur - containing glycolipid.
 The sulfate is present in ester linkage at C3 of the galactose portion
of the molecule.
 Members of this group of cerebroside sulphuric esters have been
designated as sulfatides.

19. Functions of glycolipid
 It provides energy to the cells.
 It is an essential part of cell membranes.
 It helps in determining the blood group of an individual.
 It acts as receptors at the surface of the red blood cells.
 It also functions by assisting the immune system by destroying and
eliminating the pathogen from the body.

20. References
 Fundamentals of Biochemistry Book – J.L JAIN, SUNJAY JAIN, NITIN
JAIN
 Textbook of Medical Biochemistry – MN Chatterjea, Rana Shinde