carbohydrates, definition, classification, examples

2.  To learn,
1. Definition and classification of carbohydrates
2. Monosaccharides: examples with structure
3. Disaccharides: examples with structure
4. Polysaccharides: examples with structure
2
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

3.  Carbohydrates – polyhydroxyaldehydes or
polyhydroxy-ketones of formula (CH2O)n, or
compounds that can be hydrolyzed to them.
 They are classified as
 Monosaccharide (Monomers): carbohydrates that
cannot be hydrolyzed to simpler carbohydrates; eg.
Glucose or fructose.
 Disaccharides (Dimers): carbohydrates that can be
hydrolyzed into two monosaccharide units; eg.
Sucrose, maltose
3
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

4.  Oligosaccharides – carbohydrates that can be
hydrolyzed into a few monosaccharide units.alose
e.g. raffinose, stachyose
 Polysaccharides – carbohydrates that are are
polymeric sugars; eg Starch , cellulose.
 Homopolysaccharides: made up of number of
single monosaccharide units e.g. starch, cellulose
 Heteropolysaccharides: made up of more than one
type of monosaccharide units e.g. agar, pectin,
muccopolysaccharides
4
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

5.  Aldose – polyhydroxyaldehyde, eg glucose
 Ketose – polyhydroxyketone, eg fructose
 Reducing sugar – a carbohydrate that is oxidized by
Tollen’s, Fehling’s or Benedict’s solution.
 Tollen’s: Ag+  Ag (silver mirror)
 Fehling’s or Benedict’s: Cu3+ (blue)  Cu2+ (red ppt)
 These are reactions of aldehydes and alpha-
hydroxyketones.
 All monosaccharides (both aldoses and ketoses) and
most* disaccharides are reducing sugars.
 Sucrose, is not a reducing sugar.
5
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

6.  Glucose is the most important monosaccharide.
C
C OH
H
C H
HO
C OH
H
C OH
H
CH2OH
D-glucose
O
H
C H
HO
C OH
H
C OH
H
CH2OH
CH2OH
C O
D-fructose
6
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

7.  D & L designations are based on the configuration about the
single asymmetric C in glyceraldehyde.
 For sugars with more than one chiral center, D or L refers to
the asymmetric C farthest from the aldehyde or keto group.
CHO
C
CH2OH
HO H
CHO
C
CH2OH
H OH
CHO
C
CH2OH
HO H
CHO
C
CH2OH
H OH
L-glyceraldehyde
D-glyceraldehyde
L-glyceraldehyde
D-glyceraldehyde
O H O H
C C
H – C – OH HO – C – H
HO – C – H H – C – OH
H – C – OH HO – C – H
H – C – OH HO – C – H
CH2OH CH2OH
D-glucose L-glucose
7
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

8.  Disaccharides are carbohydrates which on hydrolysis
give two molecules of monosaccharides.
 Maltose-It is a cleavage product of starch, is a
disaccharide with α (1 4) glycosidic linkage
between C1 - C4 OH of 2 glucoses. It is a reducing
sugar.
H O
OH
H
OH
H
OH
CH2OH
H
O H
OH
H
OH
H
OH
CH2OH
H
O
H
H
1
2
3
5
4
6
1
2
3
4
5
6
maltose
8
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

9.  Sucrose- Is a common table sugar, has a glycosidic
bond linking the anomeric hydroxyls of glucose &
fructose with the linkage is α (12). The full name of
sucrose is a-D-glucopyranosyl-(12)-b-D-
fructopyranose. It is a non reducing sugar.
 Lactose- Is a milk sugar, is composed of galactose &
glucose, with β (14) linkage from the anomeric OH
of galactose. Its full name is b-D-galactopyranosyl-(1
4)-a-D-glucopyranose. It is a reducing sugar.
9
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

10.  Polysaccharides: Carbohydrates which on hydrolysis
give more than ten monosaccharide units are called as
polysaccharides.
 Polysaccharides are classified as;
 Homopolysaccharides: Polysaccharides which on
hydrolysis give number of units of same
monosaccharide. E.g. Starch, Glycogen, Cellulose etc.
 Heteropolysaccharides: Polysaccharides which on
hydrolysis give number of units of more than one
monosaccharide. E.g. heparin, agar, gum etc.
10
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

11. H O
OH
H
OH
H
OH
CH2OH
H
O H
H
OH
H
OH
CH2OH
H
O
H
H H O
O
H
OH
H
OH
CH2OH
H
H H O
H
OH
H
OH
CH2OH
H
OH
H
H O
O
H
OH
H
OH
CH2OH
H
O
H
1
6
5
4
3
1
2
amylose
H O
OH
H
OH
H
OH
CH2OH
H
O H
H
OH
H
OH
CH2OH
H
O
H
H H O
O
H
OH
H
OH
CH2
H
H H O
H
OH
H
OH
CH2OH
H
OH
H
H O
O
H
OH
H
OH
CH2OH
H
O
H
O
1 4
6
H O
H
OH
H
OH
CH2OH
H
H H O
H
OH
H
OH
CH2OH
H
H
O
1
OH
3
4
5
2
amylopectin
Starch: It is made up of two units- Amylose and amylopectin.
Starch is storage of glucose in plants. Amylose is a glucose
polymer with α (14) linkages. Amylopectin is a glucose
polymer with mainly α (14) linkages, but it also has
branches formed by α (16) linkages.
11
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

12. cellulose
H O
OH
H
OH
H
OH
CH2OH
H
O
H
OH
H
OH
CH2OH
H
O
H H O
O H
OH
H
OH
CH2OH
H
H O
H
OH
H
OH
CH2OH
H
H
OH
H O
O H
OH
H
OH
CH2OH
H
O
H H H H
1
6
5
4
3
1
2
Glycogen- the glucose storage polymer in animals is similar in
structure to amylopectin.
But glycogen has more α(16) branches.
The highly branched structure permits rapid glucose release
from glycogen stores, e.g., in muscle during exercise.
Cellulose- a major constituent of plant cell walls, consists of
long linear chains of glucose with β(14) linkages
12
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES

13. “In a day, when you don't come
across any problems - you can be
sure that you are travelling in a
wrong path”.
13
PHARM. BIOCHEMISTRY/ S Y B PHARM/ VSV/ CARBOHYDRATES