POLYSACCHARIDES OR OLIGOSACCHARIDES

POLYSACCHARIDES OR OLIGOSACCHARIDES 

• Polysaccharide is an important class of biological polymers. Their function in living organisms is usually either structure- or storage-related.
• Starch is a polymer of glucose is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopetcin.
• In Animals, the structurally similar glucose polymer is the more densly branched glycogen, sometimes called 'animal starch'.
• Glycogen's properties allow it to be metabolized more quickly, which suits the active lives of moving animals.
• Structural Polysaccharides: Cellulose, Pectin and Chitin
• Cellulose is used in the cell walls of plants and other organisms, and is said to be the most abundant organic molecule on earth.
• It has many uses such as a significant role in the paper and textile industries, and is used as a feedback for the production of rayon (via viscose process),cellulose acetate, celluloid, and nitrocellulose.
• Chitin has a similar structure, but has nitrogen-containing side branches, increasing its strength. It is found in arthropod exoskeletons and in the cell walls of some fungi.
• Chitin is also has multiple uses, including surgical threads.
• Polysaccharides also include callose or laminarin, chrysolaminarin, xylan, arabinoxylan, mannan, fucoidan, and galactomannan.
• Monosaccharides can be linked together into polysaccharides(or Oligosaccharides)in a large variety of ways.
• Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed.
• Pectins are a family of complex polysaccharide that contain 1,4-linked α-D-galactosyluronic acid residues.
• They are present in most primary cellwalls and in the non-woody parts of terrestrial plants.

STORAGE POLYSACCHARIDE-GLYCOGEN

• Glycogen serves as the secondary long-term energy storage in animals and fungal cells, with the primary energy stores being held in adipose tissue.
• Glycogen is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach.
• Glycogen is the analogue of starch, a glucose polymer in plants, and is sometimes referred to as animal starch, having a similar structure to amylopectin but more extensively branched and compact than starch.
• Glycogen is a polymer of α(1--->4) glycosidic bonds linked, with α(1--->6)-linked branches.
• Glycogen is found in the form of granules in the cytosol/cytoplasm in may cell types, and plays an important role in the glucose cycle.
• Glycogen forms an energy reserves that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact than the less immediately available energy reserves of triglycerides(lipids).
• In the Liver hepatocytes, glycogen can compose up to eight percent(100-120 g in an adult) of the fresh weight soon after a meal.
• Only glycogen stored in the liver can be made accessible to other organs. In the muscles, glycogen is found in the kidneys, and even smaller amounts in certain glial cells in the brain and white blood cells.
• The Uterus also stores glycogen during pregnancy, to nourish the embryo.
• Glycogen is composed of a branched chain of glucose residues. It is stored in liver and muscles.

          1. It is an energy reserves for animals.

          2. It is the chief form of carbohydrate stored in animal body.

          3. It is insoluble in water. It turns red when mixed with iodine.

          4. It also yields glucose on hydolysis.