Medical Biochemistry and Molecular
Biology
CARBOHYDRATE CHEMISTRY
2
By
Ayman Elsamanoudy
Objectives (ILOs)
I.
to study the definition, classification of
carbohydrates
II. to know the biological importances of
carbohydrates.
III. to know the important body structure formed
by carbohydrate molecules and study its
functions .
IV. to understand how any disorder in
carbohydrates structure or function leads to
disease.
3




Carbohydrates are :
Organic compounds composed of C.H.O.
Contain more than hydroxyl group.
Contain active carbonyl group ;aldehyde at C1 or
ketone group at C2.
 Generally but not always the hydrogen and oxygen
in carbohydrates are present in the proportion of
2H and one oxygen atoms as in water.
4
 Definition:
Carbohydrates are polyhydroxy aldehydes or
polyhydroxy ketones and compound giving them
on hydrolysis
5
Function of carbohydrates
1. They serve as energy stores and fuels.
2. They enter in the structure of cell membranes.
3. Pentose sugars (ribose and deoxyribose) enter in the
structure of nucleic acids.
4. Carbohydrates enter in the structure of glycoproteins and
glycolipids.
5. Carbohydrates play important roles in recognition
between cell types or recognition of cellular structures by
other molecules.
NB: Recognition events are important in normal cell
growth, fertilization and transformation of cells.
6
Classification
Monosaccharides Disaccharides
Diff
The
simplest 2
carbohydrates.
They
contain
only
one sugar unit .
-cannot
hydrolysed
Oligosaccharides
Polyosaccharides
monsacch. 3-10 monsacch. Units linked to More
than
Units linked to each other by glycosidic bond
monsacch.
each
linked to each other
other
by
Glucose ….
by glycosidic bond
Sucrose
Starch …….
be
into
Lactose……
& 1-Maltotriose = 3 glucose units
2-Raffinose
(tri-saccharide=
glucose+glactose+fructose)
7
Units
glycosidic bond
simpler units
Ex.
10
Monosaccharides
 Are carbohydrates which, contain only one sugar
unit and cannot be hydrolyzed into smaller units
( the simplest form of carbohydrates).
 They are further classified according to:
1. Number of carbon atoms contain.
2. Whether they are aldehydes or ketones.
3. According to number of carbon atom as well as
adlehydes and ketones.
8
9
Number of Carbons
(Generic
monosaccharide
name)
Aldose Functional
Group
Ketone Functional
Group
3
(Triose)
Aldotriose
Ketotriose
Triulose
Aldotetrose
Ketotetrose
Tetrulose
Aldopentose
Ketopentose
Pentulose
Aldohexose
Ketohexose
Hexulose
4
(Tetrose)
5
(Pentose)
6
(Hexose)
10
Aldoses
Ketoses
12
Structural formula of monosaccharides
A) Straight (open) chain formula :
B) Cyclic structural formula .
1-Fischer projection form:
2-Haworth form
1-simple chain
formula
(Acyclic form)
2- Cyclic structure formula:
In the solution, the sugar which has an aldehyde group undergoes the
following:Hydration of aldehyd group to form aldenol group>>>>>then
condensation between OH group of aldenol and OH of C4 or C5 to form ring
structure
.
a-Fischer projection formula:the
b- Haworth formula:
aldhyde or ketone group react
Which may be : pyranose or
with one OH group to form
furanose
hemiacetal or hemiketal

Steps of the cyclic form construction:
1. Hydration of aldehyde or keto group to
form aldenol or ketonol group producing
aldenol or ketonol form of monosacharide.
Furan ring
H
HO
H
CHO
H
C
OH
HO
C
H
H
C
OH
H
C
OH
HO
+
CH2OH
D-Glucose
H2O
H
H
OH
C
H
C
OH
HO
C
H
H
C
OH
H
C
OH
 (or) 
 HO
CH2OH
D-Glucose aldenol,
unstable
H
HO
H
O
H
 (or)
Furan ring
CH2OH
HO
C
OH
HO
C
H
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
+
CH2OH
D-Fructose
H2O
HO
C
HO
C
H
C
H
C
CH
CH2OH
C=O
CH
 (or) -D-F
OR
CH
 HO
CH2OH
D-Fructose ketonol,
unstable
O
+
C
HO
C
H
C
H
C
H2C
 (or) -DPyran ring
Then
2- The OH group from the aldenol group condenses
with the OH :
on C4 or C5 of the aldo-sugar to forms a ring or
hemi-acetal structure with the liberation of H2O
again.
 Keto-sugar condenses only with C5 or with C6
giving Hemiketal form .
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 The aldehyde or
ketone group can react
with a hydroxyl group
to form a covalent
bond.
 An aldehyde reacts
with a hydroxyl group
creates a hemiacetal.
 A ketone reacts with a
hydroxyl group to
form a hemiketal.
19
 Haworth's formula:
 Because Fisher’s formula could not explain some of
the chemical and physical characteristics of sugars,
Haworth put forth his formula.
 . C and O atoms of the ring are drawn in the plane of
the page.
 H and OH or other side groups are written on
perpendicular plane.
 All groups located on the left side of fisher’s are
written upwards. All groups located on the right
side of fisher’s are written downwards Except in
Last C in the ring .
5 membered oxy ring
22
6 membered oxy ring
23
24
MCQs
The aldose sugar is
(A) Glyceraldhyde
(B) Ribulose
(C) Erythrulose
(D) Dihydoxyacetone
25
A triose sugar is
(A) Glycerose
(B) Ribose
(C) Erythrose
(D) Fructose
A pentose sugar is
(A) Dihydroxyacetone
(B) Ribulose
(C) Erythrose
(D) Glucose
26
. Ribulose is a these
(A) Ketotetrose
(B) Aldotetrose
(C) Ketopentose
(D) Aldopentose
A carbohydrate, commonly known as dextrose is
(A) Dextrin
(B) D-Fructose
(C) D-Glucose
(D) Glycogen
27
Which of the following is a keto sugar
A) Galactose
B) Fructose
C) Glucose
D) Mannose
28
Glycosidic bond is absent in
A) Disacharide
B) oligosacharide
C) Monosacharide
D) Polysacharide
29
Hydration of glucose leads to formation of
A) Stable alcohol
B) Unstable aldenol form of glucose
C) Direct cyclization of glucose
D) No effect
30
Fructofuranose is
A) Straight chain formula of
fructose
B) Fischer projection formula of
fructose
C) Ketenol form of fructose
D) 6 membered oxy ring of
fructose
31
The predominant form of glucose in
solution is
(A) Acyclic form
(B) Hydrated acyclic form
(C) Glucofuranose
(D) Glucopyranose
32
Asymmetric carbon atom (chiral carbon)
 Def: It is a carbon atom which is attached to 4
different group or atoms e.g. middle carbon of
glyceraldhyde.
 Any substance having asymmetric carbon atom
posses the following:
I. Show optical activity.
II. Show optical isomerism (stereoisomerism)
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34
Optical activity
 DIFF:It is the ability of the compound to rotate
plane polarized light either towards the right or
towards the left.
 Plane polarized light: is an ordinary light after
passing through special type of prism called Nicols
prism (CaCO3), the light emerging form such
prism vibrate in a single plain.
35
Types of optically active sugar solutions
A. If the compound rotate plane polarized light to the right, it
is called >>>>dextrorotatory, d or (+).
Example: Glucose is dextrorotatory so it is sometimes called
dextrose.
B. If the compound rotate plane polarized light to the left, it
is called>>>>>. levorotatory, l or (-).
Example: Fructose is levorotatory so it is sometimes called
levulose.
NB :All monosaccharides are optically active, except
dihydroxy acetone, this is due to the presence of
asymmetric carbon atoms.
36
Measurement of optical activity




By : Polrimeter or Polriscope
Composition :
1- source of light (Na light).
2-A Nicol prism(polarizer):it converts ordinary
scattered light into PPL.
 3- A glass tube in which the exmined solution will
be done.
 4- Analyzer which determine the angel of rotation.
 5- Detector
37
38
39
 Specific rotation

It is the angle of rotation specific for each
optically active substance when the
concentration of substance is 100 g/dl and the
length of measuring tube is 10 cm using Na
light at 20 Ċ.
 Examples :
 The specific rotation :
1. for glucose is + 52.5 &
2. for fructose is - 91.
40
Factors affecting specific rotation
1.
2.
3.
4.
Type of light.
Length of the tube.
Nature and concentration of substance.
Temperature.
41
Optical isomerism
 Def :Compounds having the same structural
formulae (same chemical group) but differ in the
way these groups are attached in space around only
one of its asymmetric carbon atom.
 The number of optical isomers = 2n where n =
number of asymmetric carbon atoms in a molecule.
42
Types of isomerism of monosacharides:





1-Enantiomers: (D & L configuration).
2-Anomers or α and β isomer.
3-Epimers.
4-Aldose and ketose isomers .
5-Pyranose and furanose isomers
43
Enantiomers: (D & L) isomers
 Concept: Two isomers which are mirror images .
 Reffered to : prelast carbon which is the last asymetric
C atom .
 Types of enantiomers :
 1- D form: OH attached to the right of prelast C.
 2-L form: OH attached to the left of prelast C
 Description :They differ in all carbons (mirror image)
but D & L configuration is according to H – OH
orientation in the pre-last C.
 NB: The great majority of the sugars in humans are Dsugars
44
45
46
47
48
Anomers :α and β isomer
 Concept:These are isomers that differ in position of OH
group at the anomeric carbon atom.
 Reffered to: anomeric C atom
 Def of annomeric C atom: is the asymmetric carbon atom
obtained from active sugar group in the cyclic structure .
 Position of anomeric C:C1 in aldose and C2 of ketose).
 Types of anomers :
 1- α sugar : OH group attached to the anomeric carbon is
on the right side.
 2- β sugar. OH group attached to the anomeric carbon is
on the left side.
49
50
51
52
Epimers
 Concept :If two monosaccharides differ in
configuration around only one asymtetric carbon
atom other than anomeric C& the prelist C atom
,((the epimeric carbon))>>>> they are defined as
epimers of each other.
 Referred to: epimeric carbon .
 Def of epimeric carbon : asymtetric carbon atom
other than anoneric& the prelist C atoms.
 Examples : usually erpimers are described in pairs :
.
Glucose & galactose are C4 epimer. .
53

Glucose & mannose are C2 epimer
54
55
Aldose and ketose isomers
 Concept :Two isomers have the same molecular
formula but differ in aldhyde group or ketone group
 Example :. glucose --- fructose

ribose --- ribulose.
56
57
Pyranose and furanose isomers
 Glucose can be present in glucopyranose and as
glucofuranose both are isomers.
58
59
60
MCQs
The number of isomers of glucose is
(A) 2
(B) 4
(C) 8
(D) 16
61
Isomers differing as a result of
variations in configuration of the —OH
and —H on carbon atoms 2, 3 or 4 of
glucose are known as
(A) Epimers
(B) Anomers
(C) Optical isomers
(D) Steroisomers
62
The most important epimer of glucose is
(A) Galactose
(B) Fructose
(C) Arabinose
(D) Xylose
63
-D-glucose and -D-glucose are
(A) Stereoisomers
(B) Epimers
(C) Anomers
(D) Keto-aldo pairs
64
Which of the following is an epimeric pair?
(A) Glucose and fructose
(B) Glucose and galactose
(C) Galactose and mannose
(D) Lactose and maltose
D-Glucose and D-glucose are related by
(A) Epimers
(B) Anomers
(C) aldose ketose isomers
(D) pyranose-furanose isomers
65
Sugar Derivatives
 They include:
I. Sugar Acids.
II. Sugar Alcohols.
III. Deoxysugars.
IV. Amino Sugars.
V. Amino sugar acids.
66
Sugar Acid.
 Def: They are the oxidation products of monosaccharides
Aldonic acids:
deff
Aldaric acids:
Oxidation of carbonyl Oxidation of the last They
group
Oxidation
Uronic acids:
to
group yields aldonic acids
both carbonyl carbon and
acid.
last hydroxyl carbon,
Glucuronic acid
L iduronic acid
67
dicarboxylic
carboxylic carbon yields uronic resulting from oxidation of
of Gluconic acid
glucose gives
are
Glucaric acid
1.Aldonic
CHO
H C
HO C
OH
H
COOH
H C
OH
bromine water, O2 HO C H
H C
OH
H C
OH
H C
OH
H C
OH
CH2OH
D-Glucose
CH2OH
D-Gluconic acid
2-Uronic
CHO
H C
HO C
CHO
OH
H
H C
OH
H C
OH
CH2OH
D-Glucose
H C
H2O2
Dil. Nitric acid
HO C
OH
H
H C
OH
H C
OH
COOH
D-Glucuronic acid
3-Aldaric
CHO
H C
HO C
COOH
OH
H
H C
OH
H C
OH
CH2OH
D-Glucose
H C
O2
Conc. Nitric acid
HO C
OH
H
H C
OH
H C
OH
COOH
D-Glucaric acid
CHO
COOH
H
C
OH
HO
C
H
OH
H
C
OH
OH
H
C
OH
H
C
OH
HO
C
H
H
C
H
C
CH2OH
D-gluconic acid
71
COOH
D-glucuronic acid
Imortance of Iduronic acid :
glycosaminoglycans
formation
(mucopolysaccharides)
Imortance of Glucuronic acid :
1. Detoxication reactions.
2. Formation
of
glycosaminoglycans
(mucopolysaccharides).
3. Metabolism of bilirubin.
4. Excretion of steroids.
72
73
L-ascorbic acid (vitamin C)
 It is a 6-carbon sugar acid.
 It is water soluble and optically active.
 Humans are unable to synthesize it and hence must
be supplied in the diet.
 It has 2 forms:

reduced form ( ascorbic acid )

oxidized form ( dehydroascorbic acid )
74
Ascorbic acid
(reduced form)
75
dehydrAscorbic acid
(oxidized form)
2-Sugar alcohols (Alditols)
 Diff: It is the product of reduction of the active
carbonyl group .
 Concept: Aldoses and Ketoses may be reduced at the
carbonyl carbon to the corresponding polyhydroxy
alcohols (sugar alcohols).
 Examples :





D-glucose
D-mannose
D-fructose
D-galactose
D-ribose
76
D-sorbitol.
D-mannitol.
D-sorbitol and D-mannitol.
D-galacticol.
D-ribitol
CHO
CH2OH
H C OH
H C OH
H C OH
H2
H C OH
H C OH
Na amalgum, H 2SO4 H C OH
CH2OH
CH2OH
Ribose
77
Ribitol
CHO
CH2OH
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H2
Na amalgum, H 2SO4
H
C
OH
HO
C
H
H
C
OH
H
C
OH
CH2OH
CH2OH
Glucose
Sorbitol
CH2OH
CH2OH
H C OH
C=O
HO C H
H C OH
H C OH
CH2OH
Fructose
78
CH2OH
H2
Na amalgum, H 2SO4
HO C H
H C OH
HO C H
OR
HO C H
H C OH
H C OH
H C OH
CH2OH
CH2OH
Sorbitol
Mannitol
 Cyclitol ( inositol)

It is a cyclic hexa hydric alcohol derived from
glucose.
 A member of vitamin B complex.
OH
3
H
4
OH
H
OH
5
H
Inositol
79
OH
OH
2
H
H
6
OH
1
H
3- Deoxysugars
 Def:They are monosaccharides with only one of its
hydroxyl groups is replaced by hydrogens i.e. there is only
one oxygen missed.
 Examples :
 2-Deoxy-D-ribose is a constituent of DNA.
80
 Fucose :6 deoxy-galactose ( it is a component of
glycoprotein
81
4- Amino sugars
Def:The hydroxyl group is replaced by an amino group at
the C-2 position.
 Importance
:Amino
sugars
are
found
in
glycosaminoglycans and glycoproteins.
 Examples :
D-glucosamine:
It is a constituent of heparin and hyaluronic acid.
D-galactosamine:
It is a constituent of chondriotin sulphate.
Mannosamine
It is a constituent of neuraminic acid and sialic acids
82
CH2OH
O
H
H
H
OH
2
OH
H
CH2OH
H
OHH
OH OH H
NH2
-D-glucoamine
83
H
CH2OHO
H
OHOH
H
2
6CHCHOH2O-SO3H
2
OH
H HOH HH
H
2 OHOH OH
H
H H HN CNHCH
2 3
- D-galactosamine
O
N-acetyl-glucosamine
OH
OH
H
OO
HH
22
6
CH2O HH
O-SO 3H
4
OH
OHH
HN C CH3
H
OH
H
H
NH-SO3H
O
sulfated N
N- acetyl-galactosamine
sulfated glucosamine galactos
5-Amino sugar acids
Def:They are condensation products of amino sugars and
some acids
Example:
Neuraminic acid
Discription: It results from a C-C bond between the C-1
of mannosamine and the C-3 of pyruvic acid.
Importance of neuraminic acid
 It is amino sugar acid present in neural tissue.
 The N-acetyl derivative of neuraminic (NANA) is
called sialic acid, which is widely distributed in
bacteria and animal systems
84
85
Monosaccharides of Biological Importance
1) Glucose (Dextrose) (Grape Sugar):
 It is the most important and famous sugar
 It is the major source of energy in humans and animals.
 Ingested carbohydrates are absorbed in the form of
glucose.
 It is converted into other sugars in the liver and other
tissues
 Examples : galactose, fructose, ribose and glycogen.
86
2)Galactose:
 It is synthesized in mammary gland to form the
disaccharide lactose (sugar of milk).
 It can be converted into glucose in the liver.
3)Mannose:
 It is a constituent of many glycoproteins and
aminosugar acids as sialic acid.
4)Fructose (Levulose) (Fruit Sugar):
 It is present in semen
 It is a constituent of disaccharide sucrose and
polysaccharide inulin.
87
 It can be
converted into glucose in the liver.
5)Ribose and deoxyribose:
 They form part of the structural backbone of
nucleic acids RNA and DNA.
6)Ribose enters in the structure of high-energy
phosphate compounds as ATP, GTP and CTP and
also in the structure of coenzymes such as NAD,
NADP, FAD and FMN.
7)Ribose phosphate, Ribulose phosphate, Xylulose
and sedoheptulose are intermediates in
carbohydrate metabolism
88
The sugar found in DNA is
(A) Xylose
(B) Ribose
(C) Deoxyribose
(D) Ribulose
The sugar found in RNA is
(A) Ribose
(B) Deoxyribose
(C) Ribulose
(D) Erythrose
89
Sorbitol is produced by reduction of :
(A) Galactose or fructose
(B) Glucose or galactose
(C) Glucose or fructose
(D) Galactose or fructose
Glucose on reduction forms
(A) Dulcitol
(B) Sorbitol
(C) Mannitol
(D) Mannitol and sorbitol
90
Glucose on oxidation does not give
(A) Glycoside
(B) Glucosaccharic acid
(C) Gluconic acid
(D) Glucuronic acid
Oxidation of galactose with conc HNO3
yields
(A) Mucic acid
(B) Glucuronic acid
(C) Saccharic acid
(D) Gluconic acid
91
Short Questions
Discuss shortly:
1. Define asymmetric carbon atom and enumerate properties
resulted from its presence.
2. Mention the physiological importances of carbohydrates.
3. optical activity (def,measurement,examples).
4. Classify sugars according to their optical activity.
5. optical isomerism(def,types)
6. Enentiomers (def,examples )
7. Anomers (def, examples)
92
8.epimers(def, examples)
9.sugar acids (def,types & example for each)
10. sugar alcohol (def & 3 examples )
11.Deoxy-sugar ( def & 2 different examples and the
importance of each one )
12.Amino acid sugar (def,example).
13.Enumerate the products of hydrolysis of sialic
acid.
14. Enumerate monosacharides of biological
importance
93
GREAT
THANKS
Ayman Elsamanoudy
10/13/2014
Ahmed A.Albadry
94