Polysaccharides lec 5 AIMC
Published on: Mar 4, 2016
Transcripts - Polysaccharides lec 5 AIMC
DR SHAMIM AKRAM
Great majority of CHO of nature occur as
> half of all organic C,50 % cellulos in wood.
Simply known as glycans.
Consists of more than 10 repeat units of
monosaccharides(upto hundruds and
thousands)or their derivatives held together by
Linear and branched polymers.
(Based on function)
Classification (Based on structure)
Consist of same type of monomers
Consist of two or more types of monomers.
sulphsates,Heparin,Blood group poly.and,S.mucoids.
Proteoglycans,Glycoproteins and Glycolipids
Agar,Vegetable gums and Pectins
Starch is a polymer consisting of D-
Starches (and other glucose polymers) are
usually insoluble in water because of the
high molecular weight, but they can form
thick colloidal suspensions with water.
Main sources of starch are rice, corn,
A storage polysaccharide in plants.
It contains two polysaccharide units,amylose
Amylose consists of long unbranched chains
of Alpha D-glucose(50-5000 glucose units)
connected by glycosidic linkages.
10%-20% of the starch in plants is in this form.
Amylose forms helices (coils) which can trap
molecules of iodine, forming a characteristic
deep blue-purple color. (Iodine is often used
as a test for the presence of starch).
STARCH — AMYLOPECTIN
Amylopectin consists of long chains of
glucose up to 1 million glucose units
connected by glycosidic linkages, with
branches every 24 to 30 glucose units
along the chain.
80-90% of starch is in this form in plants.
ACTION OF ENZYMES ON STARCH
The enzymes hydrolyzing starch are called
Saliva contains salivary amylase and
pancreatic juice contains pancreatic amylase.
These amylases are α amylases and hydrolyze
starch into maltose,isomaltose and α dextrins.
These are immediate products of hydrolysis of starch
by acids or by the enzyme amylase.
Consists of complex mixture of molecules of different
sizes and structures.
Present in the leaves of all starch producing plants.
Sweet in taste.
α- dextrins have eight α -D-glucose residues showing
mostly glycosidic linkages in addition to an
linkage at each of branching site.
Products of the reaction of glucose and the
enzyme transglucosidase from Leuconostoc
contains a (1,4), a (1,6) a (1,3) and a (1,2)
Used as plasma extenders (treatment of
Decreases vascular thrombosis.
Larger dextrans, which do not pass out of the
vessels, are potent osmotic agents, and thus
have been used urgently to treat hypovolemia.
The hemodilution caused by volume
expansion with dextran use improves blood
Intravenous solutions with dextran function
both as volume expanders and means of
nutrition. Such a solution provides an
osmotically neutral fluid that once in the body
is digested by cells into glucose and free
It is occasionally used to replace lost blood in
emergency situations, when replacement
blood is not available.
It is used in some eye drops as a lubricant.
also used as molecular sieves to separate
proteins and other large molecules (gel
component of dental plaques.
Also known as animal starch.
Stored in muscle and liver (mostly).
Present in cells as granules (high MW).
Contains both a(1,4) links and a(1,6) branches
at every 12-14glucose unit (more frequent
than in starch).
• Storage form of energy in animal.
• Stored in liver and muscle
• Stores more glucose residues per gram than starch.
• More branched and compact than starch.
• Less osmotic pressure.
• More energy in a smaller space.
• Glycogen in liver (6-8%) is higher than that in the
• Liver glycogen - first line of defense against
declining blood glucose levels especially between
A polymer consisting of long,unbranched
chains of D-glucose connected by
glycosidic linkages,may contain from
15000 glucose units in one molecule.
Group of high molecular weight
carbohydrates that resemble cellulose,but are
more soluble and easily decomposed.
besides glucose, sugar monomers in
hemicellulose can include xylose, mannose,
galactose, rhamnose, and arabinose.
Hemicelluloses contain most of the D-
pentose sugars, and occasionally small
amounts of L-sugars as well.
Xylose is always the sugar monomer
present in the largest amount
chitin is the second most abundant
Like cellulose, chitin is a structural polymer
present in the cell wall of fungi and in the
exoskeletons of crustaceans, insects and
Consists of N-acetyl-D-glucosamine units
β-(1,2) linked fructofuranoses
linear only; no branching
lower molecular weight than starch
hydrolysis yields fructose
sources include onions, garlic etc.
used as diagnostic agent for the evaluation of
glomerular filtration rate (renal function test)