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polysaccharides

everything of polysaccharides - by aditya lal
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Aditya Lal

on 23 September 2012

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Transcript of polysaccharides

BY ADITYA LAL POLYSACCHARIDES WHAT ARE POLYSACCHARIDES? Polysaccharides are long carbohydrate molecules of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water. Polysaccharides are classified according to their
structure, they mainly are-
1.homopolysaccharides
2.hetropolysaccharides HOW ARE POLYSACCHARIDES
CLASSIFIED? Homopolysaccharides-
they are mainly polymers of a
single and same repeating monosaccharide
unit. Hetropolysaccharides these are polymers of different and
repeating monosaccharide units STARCH Starch or amylum is a carbohydrate consisting of a large number of glucose units joined by glycosidic bonds.
This polysaccharide is produced by all green plants as an energy store. It is the most common carbohydrate in the human diet and is contained in large amounts in such staple foods as potatoes, wheat, maize (corn), rice, and cassava.

Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol.
It consists of two types of molecules: the linear and helical amylose and the branched amylopectin.
Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. amylose amylose is a long
unbranched chain with
200-1000 D-glucose units
held by glycosidic linkages AMYLOPECTIN It is a branched chain
with alpha glycosidic bonds
at the branching points and
alpha linkages everywhere else.
amylopectin contains a thousand
glucose units which looks like a branched tree starches DEXTRINS Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen.
Dextrins are mixtures of polymers of D-glucose units linked by α-(1-4) or α-(1-6) glycosidic bonds. Dextrins can be produced from starch using enzymes like amylases, as during digestion in the human body
It also occurs on the surface of bread during the baking process, contributing to flavor, color, and crispness Dextrins are white, yellow, or brown powders that are partially or fully water-soluble, yielding optically active solutions of low viscosity.
Most can be detected with iodine solution, giving a red coloration;
one distinguishes erythrodextrin (dextrin that colours red) and achrodextrin (giving no colour). INULIN Inulins are a group of naturally occurring polysaccharides produced by many types of plants.
Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes. Inulin is used to help measure kidney function by determining the glomerular filtration rate (GFR).
GFR is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time. Inulin is of particular use as it is not secreted or reabsorbed in any appreciable amount at the nephron allowing GFR to be calculated. Glycogen is a multibranched polysaccharide that serves as a form of energy storage in animals and fungi.
In humans, glycogen is made and stored primarily in the cells of the liver and the muscles,
and functions as the secondary long-term energy storage (with the primary energy stores being fats held in adipose tissue).
Also it is broken down to maintain blood glucose
levels GLYCOGEN Glycogen is a branched biopolymer consisting of linear chains of glucose residues with further chains branching off every ten glucoses or so.
Glucoses are linked together linearly by α(1-→4) glycosidic bonds from one glucose to the next. Branches are linked to the chains they are branching off from by α(1→-6) glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain CELLULOSE Cellulose is an organic compound with the formula (C6H10O5)n,
a polysaccharide consisting of a linear chain of several hundred to over ten thousand (1-4) linked D-glucose units

animals cannot digest cellulose , hence forms rouhage in man's diet which is important for proper bowel movement.
ruminants have bacteria in their guts to
digest cellulose. cellulase the enzyme cleaves beta glycosidic bonds. CHITIN Chitin (C8H13O5N)n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world.
It is the main component of the cell walls of fungi, the exoskeletons of arthropods such as crustaceans (e.g., crabs, lobsters and shrimps) and insects, the radulas of mollusks, and the beaks of cephalopods, including squid and octopuses.
In terms of structure, chitin may be compared to the polysaccharide cellulose and, in terms of function, to the protein keratin.
Chitin has also proven useful for several medical and industrial purposes. Glycosaminoglycans (GAGs) or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit
. The repeating unit consists of a hexose (six-carbon sugar) or a hexuronic acid,
linked to a hexosamine (six-carbon sugar containing nitrogen).

the presence of sulphate and carboxyl groups contribute to the acidity of the molecules,
making them acid mucopolysaccharides

Gags are essential components of tissue structure. the extracellular spaces of
tissues(connective tissue cartilage, skin , blood vessel, tendons) consist of
ground substances which contain GAGS MUCOPOLYSACCHARIDES HYALURONIC ACID
Hyaluronan (also called hyaluronic acid or hyaluronate or HA) is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues.

It is unique among glycosaminoglycans in that it is nonsulfated, forms in the plasma membrane instead of the Golgi, and can be very large, with its molecular weight often reaching the millions.

One of the chief components of the extracellular matrix, hyaluronan contributes significantly to cell proliferation and migration, and may also be involved in the progression of some malignant tumors. HYALURONIDASE It is an enzyme that breaks the (beta 1 )linkage of hyaluronic acid and other GAG.
This enzyme is present in high concentration is tesetes ,seminal fluid and certain snake venoms.
this enzyme has an important role in fertilization asit clears the gel found around the ovum , allowing better penetration of the sperm chondrotin sulphate

Chondroitin sulfate is a sulfated glycosaminoglycan (GAG) composed of a chain of alternating sugars (N-acetylgalactosamine and glucuronic acid).
It is usually found attached to proteins as part of a proteoglycan.
A chondroitin chain can have over 100 individual sugars, each of which can be sulfated in variable positions and quantities.
Chondroitin sulfate is an important structural component of cartilage and provides much of its resistance to compression.
Along with glucosamine, chondroitin sulfate has become a widely used dietary supplement for treatment of osteoarthritis HEPARIN
Heparin (from Ancient Greek π (hepar), liver), also known as unfractionated heparin,
highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant,
and has the highest negative charge density of any known biological molecule.
Heparin is composed of alternating units of N- sulfo D-glucosamine 6-sulfate
and glucuronate 2 sulfate DERMATIN SULFATE

Dermatan sulfate is a glycosaminoglycan (formerly called a mucopolysaccharide) found mostly in skin, but also in blood vessels, heart valves, tendons, and lungs.
It is also referred to as chondroitin sulfate B, although it is no longer classified as a form of chondroitin sulfate by most sources. The formula is C14H21NO15S.
the only diffrence is that there is inversion in the configuration around c5 of D-glucuronic acid to form L-iduronic acid keratin sulphate

Keratan sulfate (KS), also called keratosulfate, is any of several sulfated glycosaminoglycans (structural carbohydrates) that have been found especially in the cornea, cartilage, and bone.
It is also synthesized in the central nervous system where it participates both in development and in the glial scar formation following an injury.
Keratan sulfates are large, highly hydrated molecules which in joints can act as a cushion to absorb mechanical shock.

it has variable sulfate content ,
besides small amounts of mannose , fructose ,sialic acid. but it essentially consists of alternating units of N-acetylglucosamine 6 sulfate Glycoproteins are proteins that contain oligosaccharide chains (glycans) covalently
attached to polypeptide side-chains.

the functions are- GLYCOPROTEINS END Dextrins Glucose + Maltose amylase
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