biomedical importance. chemical nature, structure, classification. properties

1. CARBOHYDRATE
STRUCTURE and PROPERTIES
Whilhelmina Annie Mensah 1

2. • I would feel more optimistic about a bright
future for man, if he spent less time proving
that he can outwit Nature and more time
tasting her sweetness and respecting her
seniority.
—E. B. White, “Coon Tree,” 1977
2

3. A. Biological and medical
importance
Functions
B. Chemical nature
 Ketose and hexoses
C. Structure
Fisher , Haworth and
Comformations
D. Classification of carbohydrates
Monosaccharides
Hexoses of physiologic importance
Important sugar derivatives
Oligosaccharides: Disaccharides
Polysaccharides
Homopolysaccharides and
heteropolysaccharides
E. Properties of monosaccharides
Lecture objectives
3

4. Key Words
Saccharide: sugar
Chiral /Asymmetrical : a carbon with four groups
bounded to it.
Anomeric or carbonyl : carbon 1
Hydroxyl group: OH group
Reduction : addition of hydrogen, removal of oxygen
Oxidation : addition of oxygen, removal of hydrogen,
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5. 5
Carbohydrates are the most abundant biomolecules in nature
Present in humans, animal tissues, plants and in micro-
organisms.
Also present in tissue fluids, blood, milk, secretions and
excretions of animals.
A. Medical And Biological Importance

6. A. Medical And Biological Importance
– Functions
Serve as energy stores and fuels, and metabolic
intermediates, glucose and glycogen
Components of several animal structure and plant
structures e.g. cartilage, tendons, cellluose
A part of DNA and RNA
Part of drugs e.g. the antibiotic streptomycin
 etc.
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7. Carbohydrates ( saccharides - SUGAR) are polyhydroxy
alcohols with a aldehyde or keto functional group
Empirical formula is (CH2O)n; some also contain
nitrogen, phosphorus, or sulfur
B. Chemical Nature Of Carbohydrates
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8. C. STRUCTURE
 The structure of some carbohydrates exist in
three (3) forms
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9. Relating Fisher projection to Haworth projection(Ring)
– Groups on the right in a Fischer projection point downwards in a
Haworth projection
– Groups on the left in a Fischer projection point upwards in a
Haworth projection
C. STRUCTURE
9

10. Ring form conformations
Pyranose : 6 member ring
 furanose: 5 member ring
D. STRUCTURE
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11. D. Classification Of Carbohydrates
1. Monosaccharides
2. Oligosaccharides
2a. Disaccharides
3. Polysaccharides
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12. D. Classification Of Carbohydrates
1. Monosaccharide (simple sugar)- cannot be
hydrolyzed into simpler carbohydrates, they include
Trioses Tetroses Pentoses Hexoses Or Heptoses
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13. D. Classification Of Carbohydrates
1. Monosaccharide (simple sugar)
 Important monosaccharides, examples
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14. D. Classification Of Carbohydrates
1. Monosaccharide (simple sugars)
 Hexoses of physiologic importance
Sugar Source Clinical significance
D –glucose •Fruit Juices,
•cane sugar
•Hydrolysis of starch,
cane sugar and
lactose
Present in the urine (glycosuria) in
diabetes mellitus owing to raised
blood glucose (hyperglycemia)
D-Fructose Fruit juices , honey Hereditary fructose intolerance leads
to fructose accumulation
and hypoglycemia
D-Galactose Hydrolysis of lactose Failure to metabolize leads to
galactosemia and cataract
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15.  Biologically Important Sugar (Glucose) Derivatives
1. Sugar Acids
2. Sugar Alcohols
3. Deoxy Sugars
4. Amino Sugars
5. Glycosides.
D. Classification Of Carbohydrates
1. Monosaccharide (simple sugars)
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16. 1. Sugar Acids
 Oxidation of aldo group of sugars
produces aldonic acids. Ketoses are not
easily oxidized.
Examples
• Glucuronic acid or uronic acid :oxidation
of terminal alcohol group (–OH sixth
carbon atom of glucose
• Uronic acids are components of
mucopolysaccharides.
Oxidation
D-Glucose D-Glucoronic acid
Sugar (Glucose) Derivatives
D. Classification Of Carbohydrates
(1. Monosaccharides)
16

17. 2. Sugar alcohols
Reduction of aldose and
keto groups of sugar
produces polyhydroxy
alcohols or polyols.
Examples
– Glycerol and inositol.
– Glucose - sorbitol,
– Galactose – galactitol
– fructose are - sorbitol,
Reduction
 Sugar (Glucose) Derivatives
D. Classification Of Carbohydrates
(1. Monosaccharides)
17

18. 3. Deoxy Sugars
oxygen of a hydroxyl
group is removed
leaving hydrogen.
 Examples
– Deoxyribose: in
nucleic acids.
– Fucose : in blood
group substances.
Removal of O
from OH group
 Sugar (Glucose) Derivatives
D. Classification Of Carbohydrates
(1. Monosaccharides)
18

19. Substitution of
OH with NH3
 Sugar (Glucose) Derivatives
4. Aminosugars
Those sugars in which an
amino group is substituted
for a hydroxyl group.
Amino sugars are
components of
mucopolysaccharides, and
antibiotics
Examples
D-glucosamine
N-acetalglucosamine
D. Classification Of Carbohydrates
(1. Monosaccharides)
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20. 2. Oligosaccharides : They
consist of 2-10 monosaccharide
units. Most important
oligosaccharides are disaccharides
2a. Disaccharides : are
condensation products of two
monosaccharide units.
E.g. are maltose =glucose + glucose
sucrose = fructose + glucose
lactose = galactose + glucose
trehalose
D. Classification Of Carbohydrates
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21. 2a .Disaccharides : condensation products of two
monosaccharide units.
D. Classification Of Carbohydrates
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22. Classification Of Carbohydrates
2a. Disaccharides
 Disaccharides of physiologic importance
Sugar Source Clinical significance
Maltose Digestion by amylase or
hydrolysis of starch
Lactose Milk, May occur in urine
during pregnancy
In lactase deficiency, Lactose
intolerance causes
malabsorption which leads
to diarrhea and flatulence
Sucrose Cane and beet sugar.
Sorghum, Pineapple,
carrot roots
In sucrase deficiency,
malabsorption leads to
diarrhea and flatulence 22

23. 3. Polysaccharides: Condensation products of more
than ten monosaccharide units
They are either linear α(1-4) linkage or
 branched α (1-6) linkage polymers.
Examples
starch, glycogen, cellulose, dextran and inulin and
chitin.
Proteoglycans and glycosaminoglycans.
D. Classification Of Carbohydrates
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24. D. Classification Of Carbohydrates
24
α (1-6)
linkage
α (1-4)
linkage

25. 2b.Types of Polysaccharides are classified on the basis of the
type of monosaccharide present.
(a) Homopolysaccharides : They are entirely made up of one
type of monosaccharides. On hydrolysis, they yield only one
kind of monosaccharide
 E.g. starch, glycogen, cellulose, dextran and inulin
and chitin.
(b) Heteropolysaccharides : They are made up of more than
one type of monosaccharides. On hydrolysis they yield more
than one type of monosaccharides.
 Eg. Proteoglycans and glycosaminoglycans.
D. Classification Of Carbohydrates
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26. 2b. b.Heteropolysaccharides
Types
 Proteoglycans (Mucopolysaccharides) : consist of
protein with a repeating polysaccharide unit.
 Glycoproteins : Proteins which has less than 100
saccharide residues have been added.
 Glycosaminoglycans: a proteoglycan with the protein
portion removed
D.Classification Of Carbohydrates
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27.  2b.b.Heteropolysaccharides
Important proteoglycans or glycosaminoglycans
(GAGs)
Hyaluronic Acids: found on cell surfaces, synovial fluid
and vitrous humour
Classification Of Carbohydrates
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28.  2b.b.Heteropolysaccharides
Important proteoglycans or glycosaminoglycans (GAGs)
Chrondroitin Sulfate: found in cartilage, tendon, bone
Classification Of Carbohydrates
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29.  2b.b. Heteropolysaccharides
Important proteoglycans or glycosaminoglycans (GAGs)
Heparin : Anti-coagulant present in blood
Classification Of Carbohydrates
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30. 1. Optical isomerism
2. Optical activity
3. Epimerism
4. Hemiacetal and hemiketal formation
5. L and D forms
6. Anomers
7. Mutarotaion
8. Formation of glycosidic bonds
9. Reducing properties
E. Properties of Monosaccharides
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31.  1.Optical isomerism
 Enantiomers : They are mirror images.
E. Properties of Monosaccharides
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32. 2. Optical activity : the ability of a sugar to rotate plane
polarized light
Orientations
– right - dextrorotatory
– left -levorotatory.
– ‘+’ sign or ‘d’ indicates dextrorotation
– ‘–’ sign or 1 indicates levorotation of a sugar.
Example
D-glucose which is dextrorotatory is designated as D(+)glucose
D-fructose, which is levorotatory is designated as D(–) fructose.
Note: The letter ‘D’does not indicate whether a given sugar is dextro
or levorotatory
E. Properties of Monosaccharides
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33.  3. Epimers
 Isomers differing as a result of variations in configuration
of the OH and H on carbon atoms 2, 3, and 4 of glucose.
E. Properties of Monosaccharides
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34. E. Properties of Monosaccharides
 4. Hemiacetal or Hemiketal formation
Hemiacetal formation
• The linkage between aldehyde group and alcohol is called
as ‘hemiacetal’ linkage. Forming 6 member pyranose ring
Hemiacet
al
formationHemiacetal
formation
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35. E. Properties of Monosaccharides
 4. Hemiacetal or Hemiketal formation
Hemiketal formation
• The linkage between keto group and alcohol is called as
‘ketal linkage. Forming 5 member furanose ring
Hemiketal
formation
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36. PROPERTIES and STRUCTURE
 5. L and D forms
D sugars :compounds that have the last asymmetrical carbon in
the same orientation as D-glyceraldehyde
L sugars: Related to L-glyceraldehyde
E. Properties of Monosaccharides
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37. 6. Anomers (α & β-form )
Monosaccharides that differ in configuration of OH groups
on carbonyl carbon (C-1) or anomeric carbon.
 α-form - Right
 β-form - Left
E. Properties of Monosaccharides
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38.  7. Mutarotation
Monosaccharides containing asymmetric carbon atom rotate
plane polarized light.
The change in optical rotation when either form of glucose is
allowed to stand in solution is mutarotation
Example : exchange between α and β forms
E. Properties of Monosaccharides
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39.  8. Glycosidic bond/ linkage
(Glycosides)
Types
O- glycosidic When hydroxyl group
on anomeric carbon of a sugar reacts
with an alcohol ( or another sugar).
They exist in disaccharides,
oligosaccharides and polysaccharides
N- glycosidic : hydroxyl group on
anomeric carbon of sugar reacts with
an amine. They are present in
nucleotides, RNA and DNA.
Properties of Monosaccharides
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40. – α bond : if the
anomeric
hydroxyl is in is
below the
Hydrogen
– β bond : if the
anomeric
hydroxyl is
above the
hydrogen
 7. Types of Glycosidic bond/ linkage
Types
Properties of Monosaccharides
40

41.  9.Reducing properties
Glucose and other sugars capable of reducing
ferric or cupric ion in solution are called reducing
sugars.
They reduce and colour Benedicts and Fehlings
solution with the aldehyde group of the sugar
E. Properties of Monosaccharides
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42. A.Biological and medical importance
Functions : energy source, storage, structural, part of DNA
& RNA, component of drugs
B. Chemical nature
 Ketose and hexoses
 Empirical formular - ( CH2O)n
C. Structure
Fisher projection
 Haworth projection (Ring forms – pyranose and furanose)
 Comformations (boat and chair)
Lecture Summary
42

43. D. Classification of carbohydrates
Monosaccharides
Hexoses of physiologic importance : glucose , fructose ,
galactose
Important sugar derivatives : sugar acids, sugar alcohols,
deoxy sugars, amino sugars and glycosides
Oligosaccharides
Disaccharides of physiologic importance: lactose , sucrose,
maltose
Polysaccharides
Homopolysaccharides : chitin, cellulose, glycogen, starch
 heteropolysaccharides : Proteoglycans, glycoproteins, GAGS
Lecture Summary
43

44. E. Properties of monosaccharides
 Optical isomerism
 Optical activity
 Epimerism
 Hemiacetal and hemiketal formation
 L and D forms
 Anomers
 Mutarotaion
 Formation of glycosidic bonds
Lecture Summary
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