1 / 11

Polysaccharides

Polysaccharides. IUG, Fall 2012 Dr. Tarek Zaida. Polysaccharides. C ontain many linked monosaccharides and vary in chain length and molecular weigh. Most polysaccharides give a single mono- saccharide on complete hydrolysis.

sandyz
Download Presentation

Polysaccharides

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Polysaccharides IUG, Fall 2012 Dr. TarekZaida

  2. Polysaccharides • Contain many linked monosaccharides and vary in chain length and molecular weigh. • Most polysaccharides give a single mono-saccharide on complete hydrolysis. • The monosaccharide units may be linked linearly, or the chains may be branched. • Polysaccharides formed from pentoses are called pentosans, while the ones made from hexoses are called hexosans

  3. Comparison of Polysaccharides to Mono- & Disaccharides

  4. Examples of Polysaccharides1. Starch • Is the energy-storing carbohydrate of plants. • It is the form in which glucose is stored by plants for later use. • Is made up of glucose units joined mainly by 1,4-α-glycosidic bonds, although the chains may have a number of branches attached through 1,6- α –glycosidic bonds. • Partial hydrolysis of starch gives maltose, and complete hydrolysis gives only d-glucose.

  5. Starch can be separated into two fractions: amylose and amylopectin. • In amylose, which constitutes about 20% of starch, the glucose units (50 to 300) are in a continuous chain, with 1,4 linkages

  6. Amylopectinis highly branched. • May contain 300 to 5000 glucose units, • Chains with consecutive 1,4 links average only 25 to 30 units in length. • These chains are connected at branch points by 1,6 linkages. • Because of this highly branched structure, starch granules swell and eventually form colloidal systems in water.

  7. 2. Glycogen • Is the energy-storing carbohydrate of animals. • Like starch, it is made of 1,4- and 1,6-linked glucose units. • Glycogen has a higher molecular weight than starch (perhaps 100,000 glucose units), and its structure is even more branched than that of amylopectin, with a branch every 8 to 12 glucose units. • Glycogen is produced from glucose, transported to the liver, muscles, where it is stored for later use. • Glycogen helps maintain the glucose balance in the body by removing and storing excess glucose from ingested food and later supplying it to the blood when various cells need it for energy.

  8. 3. Cellulose • Celluloseis an unbranched polymer of glucose joined by 1,4-b-glycosidic bonds.

  9. Other Polysacchrides 4. Dextrin: Produced during the hydrolysis of starch. 5. Heparin: Made up of repeated units of glucuronic acid and glucosamine, used as a blood anti-coagulant. Is the strongest organic acid in the body. 6. Dextran: produced by bacteria when grow on sucrose.

  10. 7. Pectin: Obtained from fruits and berries, used in making jellies. • They are linear polymers of d-galacturonic acid, linked with 1,4-α-glycosidic bonds.

More Related