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

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

3.  Definition:
Carbohydrates are polyhydroxy aldehydes or
polyhydroxy ketones and compound giving them
on hydrolysis
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4.  Carbohydrates are :
 Organic compounds composed of C.H.O.
 Generally but not always the hydrogen and oxygen
in carbohydrates are present in the proportion of
2H and one oxygen atoms as in water.
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5. Classification
Monosaccharides Disaccharides Oligosaccharides Polyosaccharides
Diff The simplest
carbohydrates.
They contain only
one sugar unit .
-cannot be
hydrolysed into
simpler units
2 monsacch.
Units linked to
each other by
glycosidic bond
3-10 monsacch. Units linked to
each other by glycosidic bond
More than 10
monsacch. Units
linked to each other
by glycosidic bond
Ex. Glucose …. Sucrose &
Lactose……
1-Maltotriose = 3 glucose units
2-Raffinose
(tri-saccharide=
glucose+glactose+fructose)
Starch …….
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6. 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. Whether they are aldehydes or ketones.
2. Number of carbon atoms contain.
3. According to number of carbon atom as well as
aldehydes and ketones.
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7. 7

8. 8
Number of Carbons
(Generic
monosaccharide
name)
Aldose Functional
Group
Ketone Functional
Group
3
(Triose)
Aldotriose Ketotriose
4
(Tetrose)
Aldotetrose Ketotetrose
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(Pentose)
Aldopentose Ketopentose
6
(Hexose)
Aldohexose Ketohexose

9. Aldoses

10. 10
Ketoses

11. 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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12. 12

13. 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 its
waves pass in one direction by the action of special
prism called Nicols prism (CaCO3),
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14. 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.
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15. 10/14/2014 15Ahmed A.Albadry
GREAT
THANKS
Hussein Abdelaziz