1. Carbohydrates or Saccharides
• most abundant biological molecules
• contain primary three atoms - C, H, O
• general formula, (CH2O)n where n > 3
• monosaccharide = basic carbohydrate unit
• polysaccharide = polymeric form
• structural variation of carbohydrates is
fundamental to their biological activity
1. Monosaccharides
2. Polysaccharides
3. Glycoproteins
Outline:

2. Monosaccharides - definitions
• Monosaccharides are aldehyde or ketone
derivatives of straight-chain polyhydroxy
alcohols containing at least 3 carbon atoms.
• Aldose = carbohydrate containing an aldehyde
• Ketose = carbohydrate containing a ketone
Carbon atoms
in alcohol Name
3 triose
4 tetrose
5 pentose
6 hexose
7 heptose
. .

3. Monosaccharides - 3, 4, 5 carbon aldoses
H
Aldotriose Aldotetroses
CHO
C OH
H C OH
H C OH
CH2OH
H
CHO
C OH
HO C H
H C OH
CH2OH
CHO
HO C H
H C OH
H C OH
CH2OH
D-Ribose
(Rib)
D-Arabinose
(Ara)
D-Xylose
(Xyl)
H
CHO
C OH
H C OH
CH2OH
D-Erythrose
HO
CHO
C H
H C OH
CH2OH
D-Threose
H
CHO
C OH
CH2OH
D-Glyceraldehyde
Aldopentoses
Fischer
projections

4. Monosaccharides - 6 carbon aldoses
H
CHO
C OH
HO C H
H C OH
H C OH
CH2OH
CHO
HO C H
HO C H
H C OH
H C OH
CH2OH
CHO
H C OH
HO C H
HO C H
H C OH
CH2OH
CHO
H C OH
H C OH
H C OH
H C OH
CH2OH
D-Allose D-Glucose
(Glc)
D-Mannose
(Man)
D-Galactose
(Gal)
Aldohexoses

5. Monosaccharides - ketoses
Ketotriose Ketotetrose
CH2OH
C O
H C OH
CH2OH
D-Erythrulose
CH2OH
C O
CH2OH
Dihydroxyacetone
Ketopentoses
CH2OH
C O
H C OH
H C OH
CH2OH
CH2OH
C O
HO C H
H C OH
CH2OH
D-Ribulose D-Xylulose
Ketohexoses
CH2OH
C O
HO C H
H C OH
H C OH
CH2OH
CH2OH
C O
H C OH
HO C H
H C OH
CH2OH
D-Fructose D-Sorbose

6. Configuration and Conformation
Alcohols can react
with aldehydes or
ketones to form
hemiacetals or
hemiketals.
O H
+ C
R OH R' C
H
O
OH
R'
R
hemiacetal
O R''
+ C
R OH R' C
R''
O
OH
R'
R
hemiketal
The hydroxy group and the aldehyde (or ketone) of
monosaccharides can react intramolecularly to form
cyclic hemiacetals (or hemiketals).

7. Haworth Projections
H
CHO
C OH
HO C H
H C OH
H C OH
CH2OH
D-Glucose
CH2OH
H
H O
OH
H
OH
H
OH
H OH
H
= O
OH
H
H
CH2OH
H
OH
OH
H OH
CH2OH
OH
HOH2C
H
O
H HO
OH H
CH2OH
C O
HO C H
H C OH
H C OH
CH2OH
D-Fructose
CH2OH
O
HOH2C
H
OH
H HO
OH H
=
a-D-Glucopyranose
a-D-Fructofuranose

8. Cyclic Sugars have two Anomeric Forms
H
CHO
C OH
HO C H
H C OH
H C OH
CH2OH
D-Glucose
CH2OH
H
H O
OH
OH
H
H
OH
H OH
b-D-Glucopyranose
CH2OH
H
H O
OH
H
OH
H
OH
H OH
a-D-Glucopyranose

9. Monosaccharides are conformationally variable
Two chair conformations of b-D-glucopyranose:
HO
O
H
H
HO
H
H OH
H
OH
OH
OH
O H
OH
H
OH
H
OH
H
OH
H
Two chair conformations of a-D-glucopyranose:
HO
O
H
H
HO
H
H OH
HO
H
OH
H
O OH
OH
H
OH
H
OH
H
OH
H

10. Monosaccharide Derivatives
H
CHO
C OH
HO C H
H C OH
H C OH
COOH
D-Glucuronic acid
Oxidations:
H
COOH
C OH
HO C H
H C OH
H C OH
CH2OH
D-Gluconic acid
Reductions:
H
CH2OH
C OH
H C OH
H C OH
CH2OH
H
CH2OH
C OH
HO C H
H C OH
CH2OH
D-Ribitol D-Xylitol
H
Amino Sugars:
CH2OH
C OH
CH2OH
D-Glycerol
H
CH2OH
H
HO
CH2OH
H
OH
OH
H
HO OH
H H
H
OH
H OH
myo-Inositol
H O
HO
H
OH
H
OH
H NH2
a-D-Glucosamine
HO O
H
H
OH
H
H NH2
a-D-Galactosamine

11. Glycosides
The anomeric carbon can condense with alcohols
CH2OH
H
H O
HO
H
OH
H
OH
H OH
a-D-Glucose
+ CH3OH
( R-OH )
CH2OH
H
H O
HO
H
CH2OH
H + + H2O
OCH3
H
OH
H OH
Methyl-a-D-Glucoside
H O
HO
OCH3
H
H
OH
H OH
Methyl-b-D-Glucoside
( O-R )
( O-R )
to form a-glycosides and b-glycosides.

12. Polysaccharides (or Glycans)
• Homopolysaccharides - consist of one type of
monosaccharide
• Heteropolysaccharides - consist of more than one type of
monosaccharide
• Polysaccharides form branched as well as linear polymers.
• Complete description of an oligosaccharide includes:
- identity of the monosaccharides
- anomeric forms
- linkages of all its component monosaccharides

13. Disaccharides - simplest polysaccharides
Lactose
occurs naturally in milk
disaccharide of galactose
and glucose
6 6
CH2OH
H
H O OH
1b 1b
H
H
OH
H OH
b-D-Glucose
CH2OH
H
HO O
H
OH
H H
H OH
b-D-Galactose
O
Systematic Name: O-b-D-galactopyranosyl-(1®4)-D-glucopyranose
(1®4) designates that the glycosidic bond links C1 of galactose
with C4 of glucose
Lactose has a free anomeric carbon on the glucose end. This is an
example of a reducing sugar, and it can readily reduce mild
oxidizing agents.

14. Sucrose
Sucrose
most abundant dissacharide
common table sugar
major form of carbohydrate
transported in plants
6
CH2OH
H
H O H
H
OH
HOH2C H
H HO
1a 2b
HO CH2OH
H OH
a-D-Glucose
OH H
Systematic Name: O-a-D-glucopyranosyl-(1®2)-b-D-fructofuranoside
O
a-D-Fructose
O
The anomeric carbon of glucose and the anomeric carbon
of fructose participates in the glycosidic bond.
6
5

15. Structural Polysaccharide - Cellulose
• Plants have rigid cell walls to withstand osmotic pressure
differences and for load-bearing functions.
• Cellulose is the primary structural component of plant cell
walls.
• Cellulose is a linear polymer of up to 15,000 D-glucose
residues linked by b(1®4) glycosidic bonds.
CH2OH
CH2OH
[ H O
H
H OH
H
O H
]
H OH
b-D-Glucose
O
H O
H
H
OH
H OH
b-D-Glucose
n

16. Storage Polysaccharide - Starch
• Starch is a mixture of glycans that plants synthesize as
their principal food reserve.
• Composed primarily of a-amylose and a-amylopectin.
• The a-amylose is a linear polymer of glucose residues
linked by a(1®4) bonds.
H [ ]
n
CH2OH
H
H O
H
OH
H OH
CH2OH
H
H O
a-D-Glucose
H
OH
H OH
a-D-Glucose
O
H
O
a-amylose
Fig. 8-10
Saliva contains amylase which hydrolyzes
the a(1®4) bonds of starch.

17. Amylopectin and Glycogen
- branched polysaccharide
• Amylopectin in plants and Glycogen in animals consist
mainly of a(1®4)-linked glucose residues but is a branched
molecule with a(1®6) branch points.
a (1®6) branch point a(1®6) branch point
n
Amylopectin in plants
O
H
CH2OH
H
OH
H OH
H
]
O
H
[ O
H H
O
CH2
H
OH
H OH
H
O
O
. . . .
. . . .
. . . .
[
a(1®6) branch points every
24 to 30 glucose residues
n
Glycogen in animals
O
H
CH2OH
H
OH
H OH
H
]
O
H
[ O
H H
O
CH2
H
OH
H OH
H
O
O
. . . .
. . . .
. . . .
[
a(1®6) branch points every
8 to 12 glucose residues

18. Glycoproteins
• Many proteins are actually glycoproteins with carbohydrates
(varing from <1% to >90%).
• Polypeptide chain is synthesized under genetic control.
• The carbohydrate is added by posttranslational modification.
Proteoglycans =
complex mixture
consisting of
proteins and
glycosaminoglycans.
a proteoglycan
Fig. 8-13