Membrane Carbohydrate a brief study

MEMBRANE MEMBRANE CARBOHYDRATECARBOHYDRATE

SWEET MYSTERY OF LIFE……..

CarbohydratesCarbohydrates• Polyhydroxy aldehyde or ketonePolyhydroxy aldehyde or ketone• Most abundant biomolecules on earth.Most abundant biomolecules on earth.• Photosynthesis fixes 100 billion ton of Photosynthesis fixes 100 billion ton of

COCO22 and and

HH22O into Carbohydrate annuallyO into Carbohydrate annually• Source of energy via Glycolysis, Krebs Source of energy via Glycolysis, Krebs

cyclecycle• Insoluble carbohydrate serve as Insoluble carbohydrate serve as

structure and protective element structure and protective element

CARBOHYDRATE

STRUCTURALCARBOHYDRATE

e.g. Cellulose, Chitinetc.

STORAGECARBOHYDRATE

e.g. Starch, Glycogen etc.

GLYCOCONJUGATE ORMEMBRANE CARBOHYDRATEe.g. Glycolipid, Glycoprotein

etc.

MEMBRANE CARBOHYDRATE

• Bound to membrane via lipid or protein• Present on both side but can vary e.g. glycolipid generally present on outer half membrane but glycoprotein on both the side.• Concentration vary with membrane to membrane• Serve as destination labels for proteins• Mediators of specific cell to cell interaction

BASED ON THE CONJUGATE

GLYCOPROTEIN PROTEOGLYCANGLYCOLIPID

LIPO--POLYSACCHARIDE

GLYCOPROTEIN

• Oligosaccharides of varying complexity joined to protein

• Present on the outer face of plasma membrane, golgi complex, lysosome, secretory granule

• Sugar portion less monotonous than glycosamine of proteoglycan

• Rich in information, highly specific sites for recognition

• High-affinity binding to protein

PROTEOGLYCAN

• Glycosaminoglycan covalently bound to membrane protein

• Glycosaminoglycan moiety predominates the proteoglycan

• Biological activity is due to glycosamine moiety

• Major component of CARTILAGE

GLYCOLIPID

• membrane lipids with hydrophilic end are oligosaccharide

• Generally present on outer side of membrane

• Oligosaccharide motif is smaller but very diverse with cell to cell.

• Responsible for Human blood group type A, B, AB & O

e.g. Ganglioside, Digalactosyldiglyceride etc.

LIPOPOLYSACCHARIDE

• As glycolipid are absent in bacteria(-ve), it is there

• Sugar motif is larger than lipid

• Act as endotoxin• responsible for

immune response in human

FUNCTION OF MEMBRANE FUNCTION OF MEMBRANE CARBOHYDRATAESCARBOHYDRATAES

Functions in cell - cell recognition-glycoprotein serve as identification tags that are specifically recognized by other cells.

Mechanism through which cell recognizes other cells. cell surface contain both glycosyl transferase & their oligosaccharide substrate binding of each other’s oligosaccharide to glycosyl transferase result in adhesion,

important in cell sorting and organization in tissue and organ development

important for recognition and rejection of foreign cells by the immune system (give a “fingerprint” -tissue rejection)

Some adhesion between cells in the reception of signal molecules

give rise to A, B, and O blood groups because of glycolipid present on the RBC

GLYCOPROTEIN:- Cell Receptor as point of attachment for other cells, toxin, virus, hormone and many other molecule

CONCLUSION• A great majority of proteins and many of lipids are glycosylated. Many of their structures are to be revealed and their distinct function understood.

• Information embedded in oligosaccharide structure, decoded by specific receptors mediate many vital biological processes.

• Impaired glycosylaton may cause diseases and be disease specific.

• Surface oligosaccharides show antigenic properties and are receptor specific.

• Sugar structure change during development and ageing, as well as in response to environmental factors.

• Understanding glycobiology will help understanding and treating diseases.

REFERENCE:-

1. Robert K. Murray, Daryl K. Granner & Victor W. Rodwell: "Harper's Illustrated Biochemistry 27th Ed.", p. 526, McGraw-Hill, 2006

2. Biochemistry 5thE 11.3. Carbohydrates Can Be Attached to Proteins to Form Glycoproteins

3. Molecular Biology of the Cell (3rd Edition). Alberts B, Bray D, Lewis J, Raff M, Roberts K, Watson JD. Garland Publishing

4. Rittig MG et al (2004). "Smooth and rough lipopolysaccharide phenotypes of Brucella induce different intracellular trafficking and cytokine/chemokine release in human monocytes". Journal of Leukocyte Biology 5 (4): 196–200. PMID 12960272

5. Netea M et al (2002). "Does the shape of lipid A determine the interaction of LPS with Toll-like receptors?". Trends Immunol 23 (3): 135–9. doi:10.1016/S1471-4906(01)02169-X. PMID 11864841

6. WWW.PUBMEDCENTRAL.GOV7. WWW.SCIENCEDIRECT.COM8. www. journalseek.net/cgi-bin/journalseek/journalsearch.cgi?

field=issn&query=0282-0080

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