Oligosaccarides and
Polysaccharides
Complex
Carbohydrates
Lactose, a disaccharide
HO
CH2OH
O
HO
CH2OH
O
HO
HO

HO
CH2OH
O
O
HO
HO
OH
galactose
hydrolysis
 and 
and
lactose (from milk)
4-O-(-D-galactopyranosyl)- or-D-glucopyranose
OH
 and 
HO
CH2OH
O
HO
HO
HO
glucose



a reducing sugar; exhibits mutarotation
1,4-acetal linkage between 2 monomeric sugars
acidic hydrolysis yields galactose and glucose (1:1).
OH
 and 
Maltose, a disaccharide
CH2OH
O
HO
HO
HO

O
CH2OH
O
HO
HO

OH
maltose (from partial hydrolysis of starch)
4-O-(-D-glucopyranosyl)- or-D-glucopyranose



a reducing sugar; mutarotates
acidic hydrolysis yields only glucose
can be digested by humans & fermented by yeast.
Cellobiose, a disaccharide
CH2OH
O
HO
HO
HO

CH2OH
O
O
HO
HO

OH
cellobiose (from partial hydrolysis of cellulose)
4-O-(-D-glucopyranosyl)-or-D-glucopyranose


a reducing sugar; mutarotates
can NOT be digested by humans nor fermented by yeast;
CAN be digested by bacteria in ruminants and termites
(which have -glucosidase enzyme).
Sucrose, a disaccharide
HO
CH2OH
O
HO
CH2OH
O
HO
HO
HO

O
CH2OH
O
OH

HO
hydrolysis
HO
glucose
and
CH2OH
sucrose (from beets and sugar cane)
HO
HO


OH
 and 
CH2OH
O
OH
CH2OH
NOT a reducing sugar; NOT a hemiacetal;
fructose
does NOT undergo mutarotation
hydrolysis yields glucose plus fructose (called “invert sugar”
because rotation of polarized light changes sign).
Cellulose, a polysaccharide
CH2OH
O
O
HO
HO

CH2OH
O
O
HO
HO

CH2OH
O
O
HO
HO

CH2OH
O
O
HO
small section of cellulose molecule



HO
and 
OH
acid hydrolysis yields only glucose
can have thousands of monomers linked; only one anomeric
carbon; mutarotation occurs, NOT observed
rigid structure; hydrolyzed by -glucosidase enzymes.
Starch: a mixture of linear and
branched polysaccharides
CH2OH
O
HO
HO
CH2OH
O
O
HO
HO
CH2OH
O
O
HO
amylose (20%);
typically >200 units
HO

O
CH2OH
O
HO


HO
and 
OH
energy storage for plants (potatoes)
hydrolyzed readily by humans; yields only glucose.
Starch: the branched
component
CH2OH
O
HO
HO

O
HO
CH2OH
O
HO
HO
CH2OH
O

HO
O
CH2

O
O
HO
HO
CH2OH
O
O
HO
amylopectin (80%);
branches each ~25 units
a much larger and more
highly branched
polysaccharide
(GLYCOGEN) provides
energy storage in animals.
HO

O
CH2OH
O
HO
HO
and 
OH
Ethanol production

Ethanol can be produced by fermentation of simple
sugars promoted by yeast.
C6H12O6

yeast
2 CH3CH2OH + 2CO2
Corn and other grains are major sources of simple
sugars, but much more carbohydrate-containing
biomass is in the form of polysaccharides such as
cellulose.
Ethanol production

Efforts are now underway to utilize the otherwise wasted
(as a fuel source) polysaccharides by hydrolyzing them to
their component monosaccharides followed by
fermentation.

Other plant sources of both simple and complex
carbohydrates are being investigated as possible sources
of ethanol for fuel.

These include switchgrass, sugar cane, and even kudzu.
Other important carbohydrates
HOCH2
OH
O
CH2OH
O
HO
HO
HO
2-deoxyribose
(found in DNA)

AcNH
OH
N-acetylglucosamine,
polymer of which is chitin
-
OSO3
-
O2C
HO
HO
O
-
OSO3
O
O
O
OH
O2C
NH
HO
CH3
O
OSO3-
-
O
OSO3O
O
O
OH
synthetic tetrasaccharide related to chondroitin sulfate
NH
CH3
O
Cell-Surface Carbohydrates:
Blood Typing

The surface of human blood cells has proteins covalently
bound via glycoside bonds to oligosaccharides that serve
as antigens.

For a human to accept blood from a donor, their blood
types must be compatible; otherwise, agglutination
(clotting) occurs.

Compatibility depends on the identity of the sugars in the
oligosaccharides bound to the surface proteins.
Type A Blood
OH
fucose
O
H3C
galactose
O
OH
OH
CH2OH
O
O
HO
AcNH
O
CH2OH
HO
OH
N-acetylgalactosamine
N-acetylglucosamine
CH2OH
O
O
HO
AcNH
A
O
protein
Type B Blood
OH
fucose
O
H3C
galactose
O
OH
OH
CH2OH
O
O
HO
HO
O
CH2OH
HO
N-acetylglucosamine
CH2OH
O
O
HO
AcNH
OH
galactose
B
O
protein
Type O Blood
OH
fucose
O
H3C
galactose
O
OH
OH
CH2OH
O
HO
HO
N-acetylglucosamine
CH2OH
O
O
HO
AcNH
Recent research has led to isolation of a
bacterial enzyme that cleaves the sugar
bonded to the 3-position of galactose in
type A and B peptides to make O-type
O
O
(universal donor)
protein