{1st Dental Year } { BioChemistry } { Mans. University }

2. 2
Medical Biochemistry and Molecular
Biology
CARBOHYDRATE CHEMISTRY
By
Dr.HusseinAbdelaziz

3. Optical isomerism
 Def :Compounds having the same structural
formulae (same chemical group) but differ in the
arrangement of these groups in space around
asymmetric carbon atoms.
 The number of optical isomers = 2n where n =
number of asymmetric carbon atoms in a molecule.
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4. Types of isomerism of monosacharides:
 1-Enantiomers: (D & L configuration).
 2-Anomers α and β isomer.
 3-Epimers.
 4-Aldose and ketose isomers.
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5. Enantiomers: (D & L) isomers
 Concept: Two isomers which are mirror images .
 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 D-
sugars
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10. Epimers
 Concept :If two monosaccharides differ in
configuration around only one asymtetric carbon
atom, they are defined as epimers of each other.
 Referred to: epimeric carbon .
 Examples : usually erpimers are described in pairs :
. Glucose & galactose are C4 epimer. .
 Glucose & mannose are C2 epimer

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13. Aldose and ketose isomers
 Concept :Two isomers have the same molecular
formula but differ in aldhyde group or ketone group
 Example :. glucose --- fructose
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15. Sugar Derivatives
 They include:
I. Sugar Acids.
II. Sugar Alcohols.
III. Deoxysugars.
IV.Amino Sugars.
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16. Sugar Acid.
 Def: They are the oxidation products of monosaccharides
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Aldonic acids: Uronic acids: Aldaric acids:
deff Oxidation of carbonyl
group to carboxylic
group yields aldonic
acid.
Oxidation of the last
carbon yields uronic
acids
They are dicarboxylic
resulting from oxidation of
both carbonyl carbon and
last hydroxyl carbon,
Oxidation of
glucose gives
Gluconic acid Glucuronic acid
L iduronic acid
Glucaric acid

17. 1.Aldonic
CHO
C OHH
C HHO
C OHH
C OHH
CH2OH
COOH
C OHH
C HHO
C OHH
C OHH
CH2OH
bromine water, O2
D-Gluconic acidD-Glucose

18. 2-Uronic
CHO
C OHH
C HHO
C OHH
C OHH
CH2OH
CHO
C OHH
C HHO
C OHH
C OHH
COOH
Dil. Nitric acid
D-Glucuronic acidD-Glucose
H2O2

19. 3-Aldaric
CHO
C OHH
C HHO
C OHH
C OHH
CH2OH
COOH
C OHH
C HHO
C OHH
C OHH
COOH
Conc. Nitric acid
D-Glucaric acidD-Glucose
O2

20. 20
COOH
C
C
C
C
H OH
HO H
H OH
D-gluconic acid D-glucuronic acid
CH2OH
OHH
CHO
C
C
C
C
H OH
HO H
H OH
COOH
OHH

21. 2-Sugar alcohols (Alditols)
 Def: 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-sorbitol.
 D-mannose D-mannitol.
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22. 22
CHO
C
C HHO
C OHH
C OHH
CH2OH
H2
Na amalgum, H2SO4
Sorbitol
CH2OH
C OHH
C HHO
C OHH
C OHH
CH2OH
OHH
Glucose

23. 3- Deoxysugars
 Def:They are monosaccharides with only one of its
hydroxyl groups is replaced by hydrogen i.e. there is only
one oxygen missed.
 Examples :
 2-Deoxy-D-ribose is a constituent of DNA.
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24. 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.
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25. 10/22/2014 25Ahmed A.Albadry
GREAT
THANKS
Hussein Abdelaziz