Influencing policy (training slides from Fast Track Impact)
Classification of polysaccharides, gluconeogenesis and glucogenolysis.
1. G. D. RUNGTA COLLEGE OF SCIENCE & TECHNOLOGY, KOHKA, BHILAI.
BY:-
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Dr. ARUNIMA KARKUN
ASST. PROFESSOR
2. CLASSIFICATION OF POLYSACCHARIDES, GLUCONEOGENESIS
GLYCOGENOLYSIS
INTRODUCTION
WHAT ARE POLYSACCHARIDES?
GENERAL CHARACTERSTICS OF
POLYSACCHARIDES
CLASSIFICATION OF POLYSACCHARIDES
1. Homopolysaccharides
2. Heteropolysaccharides
ROLE OF POLYSACCHARIDES
GLUCONEOGENESIS
GLYCOGENOLYSIS
SUMMARY
REFERENCES
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3. CLASSIFICATION OF POLYSACCHARIDES
All organisms utilize carbohydrates important
biomolecules.
Nutrition: “carbos” are more than just starch and sugar.
The term carbohydrate is derived from the french word:
“hydrate de carbone.”
compounds composed of C, H, and O.
empirical formula: (CH2O)n.
Defination:- carbohydrate defined as
polyhydroxyaldehyde or ketone which produce
them on hydrolysis.
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4. CLASSIFICATION OF POLYSACCHARIDES
FUNCTION OF CARBOHYDRATES
Most abundant dietary source of energy (4 cal/g) for all organisms.
Participate in the structure of cell membrane & cellular functions.
Structural components of many organisms, include the fiber (cellulose) of
Plants, exoskeleton of some insects.
Storage of energy to meet the immediate energy demands of the body.
CLASSIFICATION OF CARBOHYDRATES
I. MONOSACCHARIDES- glucose, fructose.
I. OLIGOSACCHARIDES
• Di, tri, tetra, penta, upto 9 or 10
• Most important are the disaccharides-lactose, sucrose.
II. POLYSACCHARIDES OR GLYCANS
• Homopolysaccharides-starch, glycogen, cellulose
• Heteropolysaccharides
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CONT.
5. CLASSIFICATION OF POLYSACCHARIDES
Generally called glycans.
Contains a number of monosaccharide units linked by
glycosidic bonds.
CHARACTERISTICS:
Polymers (MW from 200,000).
White and amorphous products (glassy)
Not sweet.
Not reducing; do not give the typical aldose or
ketose reactions).
Form colloidal solutions or suspensions.
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POLYSACCHARIDES
7. CLASSIFICATION OF POLYSACCHARIDES
Divided into two broad groups:
(i) Homopolysaccharides-
Contains only one type of monomer.
On hydrolysis, they yield only one type of monosaccharide.
Examples: Starch, cellulose, glycogen
(ii) Heteropolysaccharides-
Contain two or more types of monomers.
On hydrolysis, they yield mixture of monosaccharides.
Examples: hyaluronic acid, chondriotin sulphate, heparin,
and mureins.
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Fig. no 1
8. CLASSIFICATION OF POLYSACCHARIDES
1. STARCH
• Two forms: amylose , amylopectin.
• 1,4-a-D-glucopyranose polymer.
• Function: plant glucose/energy storage.
• Hydrolysis glucopyranose.
• Easily digested by mammals.
• Natural starches contain 10-20% amylose and 80-90%
amylopectin.
a. Amylose - unbranched α (1-4 )
• 200 to 20 000 glucose units.
• Water soluble(15-20%).
• Stained blue by iodine.
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Homopolysaccharides-
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9. CLASSIFICATION OF POLYSACCHARIDES
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b. Amylopectin - branched
α (1-4 ) + α (1-6 )
Up to million glucose
units.
Water insoluble
amylopectin(80-
82%).
Stained red-brown by
iodine.
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STRUCTURE NO .1
STRUCTURE NO .2
CONT.
10. CLASSIFICATION OF POLYSACCHARIDES
2. GLYCOGEN
The glucose storage polymer in animals, is similar in
structure to amylopectin
But glycogen has more a(16) branches.
The highly branched structure permits rapid glucose
release from glycogen stores, e.g., in muscle during
exercise.
The ability to rapidly mobilize glucose is more essential
to animals than to plants
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S H O
OH
H
OHH
OH
CH2OH
H
O H
H
OHH
OH
CH2OH
H
O
HH H O
O
H
OHH
OH
CH2
H
H H O
H
OHH
OH
CH2OH
H
OH
HH O
O
H
OHH
OH
CH2OH
H
O
H
O
1 4
6
H O
H
OHH
OH
CH2OH
H
H H O
H
OHH
OH
CH2OH
H
H
O
1
OH
3
4
5
2
glycogen
CONT.
STRUCTURE NO .3
11. CLASSIFICATION OF POLYSACCHARIDES
3. CELLULOSE - nonbranched ß (1-4 )
• Insoluble, chemically very resistant.
• Major structural material of plants, wood, cotton.
• It is a major constituent of fiber.
• Cellulose is totally absent in animal.
• Composed of ß - D-glucose units linked by ß (1-4 ) glycosidic
bonds.
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STRUCTURE NO . 4
CONT.
12. CLASSIFICATION OF POLYSACCHARIDES
4.CHITIN
N-acetyl-D-glukosamine a ( 1-4 )
• Structural polysaccharide of exoskeleton of invertebrates (in complex with proteins
and/or CaCO3)
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D-galakturonic acid a (1-4)
• Methylesters
often side chains containing other
monosaccharides.
• Present in small fruits, plants.
STRUCTURE NO.5
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STRUCTURE NO..6
CONT
13. CLASSIFICATION OF POLYSACCHARIDES
2.HETEROPOLYSACCHARIDES
It is composed of a mixture of monosaccharides.
On hydrolysis, they yield a mixture of monosaccharides.
HETEROPOLYSACCHARIDES - are further
classified into two types:
A. NEUTRAL SUGARS.
B. MUCOPOLYSACCHARIDES .
A. NEUTRAL SUGARS.
This group Includes some hemicellulose, some gums,
mucilages & pectic substances.
Give more than one type of sugar units on hydrolysis &
sometimes non-sugar components .
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14. CLASSIFICATION OF POLYSACCHARIDES
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B. MUCOPOLYSACCHARIDES .
Mucopolysaccharides are heteroglycans made up of
polysaccharides made up of repeating units of sugar
derivatives, namely amino sugars & uronic sugar.
Commonly known as Glycosaminoglycans (GAG).
Mucopolysaccharides are essential components of tissue
structure.
Some Mucopolysaccharides are found in combination with
proteins to form Mucoproteins or mucoids or proteoglycans .
Mucopolysaccharides include hyaluronic acid ,heparin ,
dermatan sulfate, keratan sulfate.
15. CLASSIFICATION OF POLYSACCHARIDES
1.HYALURONATE (Hyaluronan) or Hyluronic acid.
It is a glycosaminoglycan with a repeating
disaccharide consisting of 2 glucose derivatives, glucuronate
(glucuronic acid) & N-acetyl-glucosamine.
The glycosidic linkages are ß (1-3) & ß (1-4).
Hyaluronidase is an enzyme present in high concentration in
testes, seminal fluid, in certain snake & insects that breaks ß(1-
4) linkages.
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H O
H
H
OHH
OH
COO
H
H O
OH H
H
NHCOCH3H
CH2OH
H
OO
D-glucuronate
O
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4
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1
23
4
5
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N-acetyl-D-glucosamine
hyaluronate
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MUCOPOLYSACCHARIDES
STRUCTURE NO..7
16. CLASSIFICATION OF POLYSACCHARIDES
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2. KERATAN SULFATE
It is a heterogeneous GAG with a variable sulfate content, besides small
amounts of mannose, fructose, sialic acid etc.
It is essentially consists of alternating units of D- galactosamine and
N-acetylglucasamine .
They are present in cartilage, bone, cornea, nail, hoofs, claws.
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STRUCTURE NO.8
CONT.
17. CLASSIFICATION OF POLYSACCHARIDES
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3.HEPARIN
Heparin is an anticoagulant (prevents blood clotting) that occurs in blood,
lung, liver, kidney, spleen etc.
Made in mast cell & released into the blood.
Heparin is composed of alternating units of N-sulfo D-glucosamine 6-
sulfate & glucoronate 2-sulfate,
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STRUCTURE NO.9
CONT.
19. GLUCONEOGENESIS
Definition: the biosynthesis of glucose primarily from pyruvate and its
precursors.
The major substrates/precursors for gluconeogenesis are lactate, pyruvate,
glucogenic amino acid, propionate & glycerol.
The liver is the major location for gluconeogenesis (about 1kg glucose
synthesized everyday).
Gluconeogenesis occurs mainly in the Cytosol, although some precursors are
produced in the Mitochondria.
This is essential cycle for the survival of humans and other animals.
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20. GLUCONEOGENESIS
Gluconeogenesis closely resembles the reversed pathway of glycolysis,
although it is not the complete reversal of glycolysis.
Essentially, 3(out of 10) reactions of glycolysis are irreversible.
The 7 reactions are common for both glycolysis & Gluconeogenesis.
The 3 irreversible steps of glycolysis are catalysed by the enzymes, namely
hexokinase , phosphofructokinase and pyruvate kinase.
These 3 stages- bypassed by alternate enzymes specific to Gluconeogenesis
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22. GLUCONEOGENESIS
These 3 stages- bypassed by alternate enzymes specific to Gluconeogenesis are below:-
1. Conversion of pyruvate to phosphophenol-pyruvate:
This takes place in two steps –
a) Pruvate carboxylase is a biotin-dependent mitochondrial enzyme that converts
Pruvate to oxaloacetate in presence of ATP & CO2.
b) In the cytosol, phosphoenolpyruvate carboxykinase converts oxaloacetate to
phosphoenolpyruvate.
2. Conversion of fructose 1,6-biphosphate to fructose 6-phosphate:
Phosphophenolpyruvate undergoes the reversal of glycolysis until fructose
1,6-biphosphate is produced.
3. Conversion of Glucose 6-phosphate to Glucose:
Glucose 6-phosphate catalyses the conversion of Glucose 6-phosphate to
Glucose.
Glycolysis & Gluconeogenesis are both spontaneous.
If both pathways were simultaneously active in a cell, it would constitute a
"futile cycle" that would waste energy .
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24. GLUCONEOGENESIS
Overall summary of Gluconeogenesis for the conversion of
pyruvate to glucose is shown below:-
Glycolysis:
glucose + 2 NAD+ + 2 ADP + 2 Pi
2 pyruvate + 2 NADH + 2 ATP.
Gluconeogenesis:
2 pyruvate + 2 NADH + 4 ATP + 2 GTP +2H+
glucose + 2 NAD+ + 4 ADP + 2 GDP + 6 Pi +6H +
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25. GLUCONEOGENESIS
IMPORTANCE OF GLUCONEOGENESIS :-
Brain, central nervous system, erythrocytes, testes & kidney medulla are
dependent on glucose for continuous supply of energy.
In fasting even more than a day gluconeogenesis must occur to meet the basal
requirements of the body.
Glucose is the only source that supplies energy to the skeletal muscle , under
anaerobic conditions.
Certain metabolites produced in the tissues accumulate in the blood e.g
lactate ,glycerol etc gluconeogenesis effectively clears them from blood.
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26. GLYCOGENOLYSIS
DEFINATION:-The degradation of stored glycogen in the liver and
muscle constitutes GLYCOGENOLYSIS.
The pathways for the synthesis and degradation of glycogen are not possible
are not reversible.
An independent set of enzymes present in the cytosol carry out glycogenolysis.
Glycogen is degraded by breaking α-1,4- & α-1,6-glycosidic bonds.
A good coordination & regulation of glycogen synthesis & its degradation are
essential to maintain the blood glucose levels.
Glycogenesis & glycogenolysis are , respectively, controlled by the enzymes
glycogen synthase & glycogen phosphorylase.
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27. GLYCOGENOLYSIS
2.ACTION OF GLYCOGEN PHOSPHORYLASE:-
The α-1,4-glycosidic bonds are cleaved sequentially by the enzyme glycogen to
yield glucose 1-phosphate.This process is called phosphorolysis.
The glycogen so formed is known as limit dextin which cannot be further
degraded by phosphorylase.
2. ACTION OF DEBRANCHING ENZYME:
The branches of glycogen are cleaved by two enzyme activities present on a single
polypeptide called debranching enzyme, hence it is a bifunctional enzyme.
Amylo α-1,4-glycosidase breaks the α-1,6-bond at the branch with a single glucose
residue and release a free glucose.
3.FORMATION OF GLUCOSE 6-PHOSPHATE AND GLUCOSE:
Through the combined action of glycogen phosphorylase and debranching enzyme
glucose 1-phosphate & free glucose in a ratio of 8:1 are produced .
Glucose 1-phosphate is converted to glucose 6-phosphate by the enzyme
phosphoglucomutase.
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29. GLYCOGENOLYSIS
Glycogen is the storage form of glucose.
The degradation of glycogen (glycogenolysis) in muscle
meets the immediate fuel requirements.
On the other hand the liver glycogen maintains the blood
glucose level.
Enzymes defects in synthesis or the degradation of glycogen
leads to storage disorders.
Von Gierke’s disease is due to the defect in the enzyme
glucose 6- phosphatase .
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30. SUMMARY
Carbohydrates are the polyhydroxyaldhyde or ketones or compounds which
produce them on hydrolysis .
Carbohydrates are broadly classified into three groups:-
MONOSACCHARIDES,OLIGOSACCHARIDES,POLYSACCHARIDES.
Polysaccharides are the polymers of monosaccharides on their derivative, held
together by glycosidic bonds.
Polysaccharides are broadly classified into two groups:-
(A)Hompolysaccharides (B)Heteropolysaccharides
The biosynthesis of glucose primarily from pyruvate and its precursors is
known as gluconeogenesis.
The degradation of stored glycogen in the liver and muscle constitutes
glycogenolysis.
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31. CLASSIFICATION OF POLYSACCHARIDES , GLUCONEOGENESIS,
GLYCOGENOLYSIS
Polysaccharides play important role in structure & storage for plants.
Polysaccharides are also help in cell envelope development in bacteria.
Polysaccharides provides exoskeleton in spiders & insects.
In fasting even more than a day gluconeogenesis must occur to meet the
basal requirements of the body.
Glucose is the only source that supplies energy to the skeletal muscle ,
under anaerobic conditions.
Certain metabolites produced in the tissues accumulate in the blood e.g
lactate ,glycerol etc gluconeogenesis effectively clears them from blood.
Glycogenolysis supplies energy to muscles & other body parts.
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32. CLASSIFICATION OF POLYSACCHARIDES , GLUCONEOGENESIS,
GLYCOGENOLYSIS
ALBERT L. LEHNINGER YEAR -2005 BIOCHEMISTRY,
2ND EDITION, FREEMAN
PUBLICATION.
L. NELSON & M. COX YEAR -2009 PRINCIPLES OF
BIOCHEMISTRY, 5TH
EDITION,STUTTGAT
PUBLICATION.
J. L. JAIN YEAR -2010 PRINCIPLES OF
BIOCHEMISTRY,
6TH EDITION,S.CHAND
PUBLICATION.
U.SATYANARAYANA ,
U.CHAKRAPANI
YEAR -2010 BIOCHEMISTRY,
6TH EDITION,UPPALA
PUBLICATION.
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