Power Point to Accompany
Principles and Applications of
Inorganic, Organic, and
Biological Chemistry
Denniston, Topping, and Caret
th
4 ed
Chapter 17
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
17-1
Introduction
• Carbohydrates are synthesized by
photosynthesis in plants.
• Grains, cereals, bread, sugar cane
• Glucose is major energy source
• A gram of digested carbohydrate gives
about 4 kcal of energy
• Complex carbs are best for diet
• USDA recommends about 58% daily
calories from carbs (not simple sugars)
17-2
17.1 Carbohydrate Types
Monosaccharides
E. g. glucose, fructose
one sugar (saccharide) molecule
Disaccharides
E. g. sucrose, lactose
Two monosaccharides linked
Polysaccharides
E. g. starch, glycogen, cellulose
Chains of linked monosaccharide
units
17-3
17.2 Monosaccharides
polyhydroxy
Aldehydes
are
aldoses
Number of carbons
Ketones
are
ketoses
3=triose
4=tetrose
5=pentose
6=hexose
17-4
Three carbon monosaccharides
D-glyceraldehyde
Is an aldotriose
CH2OH
O
C
H
H C OH
CH2OH
C O
dihydroxy acetone
CH2OH
Is a ketotriose
17-5
17.3 Stereoisomers and Stereochemistry
Prefixes D- and L- in a monosaccharide
name identify one of two isomeric
forms.
The isomers (same formula) differ in the
spatial arrangement of atoms and are
stereoisomers.
The stereoisomers D- and L- glyceraldehyde are nonsuperimposable
mirror image molecules and are called
enantiomers (a subset of
stereoisomers).
17-6
Stereoisomers and Stereochemistry
Molecules that can exist in enantiomeric
forms are said to be chiral.
Chirality in glyceraldehyde is conveyed
by a chiral (asymmetric) carbon-one
with four different groups attached.
17-7
Glyceraldehyde has a stereocenter (chiral)
carbon and thus has two enantiomers
(nonsuperimposable mirror image molelcules)
The D isomer has the OH on the stereocenter
to the right. The L isomer has the OH on the
stereocenter to the left.
O
H
Mirror
plane
Stereocenter: C
connected to
four
H C OH
different atoms
or groups
CH2OH
the D isomer
O
C
H
HO C H
CH2OH
the L isomer17-8
Optical Activity
Enantiomers are also called optical isomers.
Pasteur, in 1848, showed that enantiomers
interact with plain polarized light to rotate
the plane of the light in opposite directions.
This interaction with polarized light is
called optical activity and distinguishes the
isomers. It is measured in a device called a
polarimeter.
A discussion of plane polarized light follows.
17-9
Polarized Light-1
Normal light vibrates in an infinite
number of directions perpendicular to
the direction of travel. When the light
passes through a polarizing filter
(Polaroid sunglasses, for example) only
light vibrating in one plane reaches the
other side of the filter.
The diagram on the next slide illustrates
this idea. The diagram is of a
polarimeter, the instrument used to
measure rotation of plain polarized light.
17-10
Polarized Light-2
Analyzer polaroid
Rotated beam
polarizer
Light vibration in
many directions
Polarized light plane
being rotated in sample
tube.
Polarized light vibrating in vertical plane.
17-11
Optical Activity-again
When an enantiomer in a solution is placed
in the polarimeter, the plane of rotation of
the polarized light is rotated.
One enantiomer always rotates light in a
clockwise (+) direction and is said to be the
dextrorotatory isomer. The other isomer
rotates the light in a counterclockwise (-)
direction and is the levorotatory isomer.
Under identical conditions, the enantiomers
always rotate light to exactly the same
degree but in opposite directions.
17-12
Fischer Projections
A Fischer projection uses lines crossing
through a chiral carbon to represent
bonds projecting out of the page
(horizontal lines) or bonds projecting
into the page (vertical lines).
Compare the wedge vs the Fischer
pictures below for glyceraldehyde.
CHO
CHO
H C OH H
CH2OH
OH
CH2OH
the D isomer
CHO
CHO
HO C H HO
CH2OH
H
CH2OH
the L isomer
17-13
The D- and L-System
Monosaccharides are drawn in Fischer
projections with the most oxidized
carbon closest to the top. The carbons
are numbered from the top. If the
chiral carbon with the highest number
has the OH to the right, the sugar is D.
If the OH is to the left, the sugar is L.
Most common sugars are in the D form.
17-14
O
C
1
H
2
H C OH
3
CH2OH
2
C
O
3
HO C H
H C OH
4
1
CH2OH
D-erythrose
an aldotetrose
4
H C OH
5
H C OH
CH2OH
D-fructose
a ketohexose 17-15
6
CHO
CHO
H
C
OH
HO C H
H C OH
H
C
OH
HO C H
HO C H
H C OH
H C OH
CH2OH
CH2OH
D-glucose
D-galactose
an aldohexose an aldohexose
These diastereomers are also epimers, they
differ in configuration at only one
17-16
stereocenter (colored dot).
17.4 Biological Monosaccharides
Glucose is the most important sugar in
the human body. Its concentration in
the blood is regulated by insulin and
glucagon.
Under physiological conditions, glucose
exists in a cyclic hemiacetal form
where the C-5 OH reacts with the
aldehyde.
Two isomers (anomers) are formed
which differ in the location of the OH
on the acetal carbon, C-1. (Next slide)
17-17
Cyclic Form for Glucose
The cyclic form of glucose is shown as a
Haworth projection.
CH2OH
arrows show
electron movement
CH2OH
O H
H
H
H
OH H O
HO
H
OH
H
H
OH
HO
H
O H  form
(alpha)
H
OH
OH Pyranose
ring form
CH2OH
O OH
H
H
 form
OH H
(beta)
HO
H
H
OH
Haworth projections
17-18
Cyclic Form for Glucose-cont.
Fischer to Haworth projections
Draw ring
with O at
upper right.
O
1
H C OH
2
H C OH
3
HO C H O Groups to the
6
4
left go up on CH OH
2
H C OH
5
the
Haworth
5
O
H
H
HOCH2 C H
ring.
H
6
4
1
OH H
- D-glucose
HO
3
H
OH
OH
2
17-19
Fructose (Levulose or Fruit Sugar)
Found in honey, corn syrup, and sweet
fruits. The sweetest of sugars!
CH2OH
1
CH2OH
CH
OH
O

2
2
C
O
OH
H
3
HO 4C H
OHH
H 5C OH
CH2OH
H 6C OH
OH
CH2OH
O 
D-fructose
CH2OH
H
OHH
17-20
Galactose ( in lactose/milk sugar)
-D-galactoseamine is a component of
the blood group antigens.
1
CHO
2
H C OH
3
HO 4C H
HO C H
5
H C OH
6
CH2OH
CH2OH
HO
OH
H
OH H
OH
H
H OH
-D-galactose
17-21
Ribose
Ribose also exists mainly in the cyclic form
CHO
H C OH
H C OH
H C OH
CH2OH
CH2OH H
O
H H
OH
H
OH OH
-D-ribose
Deoxyribose has an H here
replacing the OH
17-22
Reducing Sugars
Aldehydes of aldoses are oxidized by
Benedict’s reagent, an alkaline
copper(II) solution. The blue color
fades as reaction occurs and a ppt
forms. Test measures glucose in urine.
O
H
C
H C OH +2 Cu2+
CH2OH
O
O
C
H C OH
CH2OH
+ Cu2O (red-orange)
17-23
Reducing Sugars
All monosaccharides and the disaccharides except sucrose are reducing
sugars. Ketoses can isomerize to
aldoses.
CH2OH HO CH
O CH
C OH
CO
H C OH
HO C H
HO C H
HO C H
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
CH2OH
CH2OH
CH2OH
D-fructose
enediol
D-glucose17-24
A Reduced Sugar
The most important reduced sugar is
deoxyribose. (In DNA)
O
H
C
H C H
H C OH
H C OH
CH2OH
D-deoxyribose
CH2OH
O OH
H H
H
H
OH H
-D-2-deoxyribose
17-25
17.5 Disaccharides
The anomeric OH can react with another
OH on an alcohol or sugar. Water is
lost to form an acetal.
Acetal link: R-O-C-O-R
CH2OH
H
O OH
H
OH H
HO
H
H
OH
+ CH3 OH
CH2OH
H
O O CH3
H
OH H
HO
H
H
OH Acetal
+ H2O
carbon
17-26
Disaccharides: Sucrose
Sucrose is formed by linking  D-glucose with
 D-fructose (acetal link=1) to give a 1,2
glycosidic link.
CH2OH
H
H
OH
HO
H
O H HO CH2
H 1
O
OH
2
H
O
H
OH
HO
H
CH2OH
Sucrose is table sugar and is linked to dental
caries. It is nonreducing. The glycosidic O
17-27
is part of an acetal and a ketal.
Disaccharides: Lactose
Lactose is formed by joining  D-galactose to
 D-glucose to give a 1,4 glycoside
CH2OH
HO
H
O
H
OH
H
CH2OH
O H
H
1
4
O
H
H
OH
-D-galactose
H
OH
H
OH
H
OH
-D-glucose
Lactose is milk sugar. Lactose intolerance
results from lack of lactase to hydrolyze the
17-28
glycosidic link of lactose.
Disaccharides:Galactosemia
In order for lactose to be used as an
energy source, galactose must be
converted to a phosphorylated glucose
molecule. When enzymes necessary
for this conversion are absent, the
genetic disease galactosemia results.
People who lack the enzyme lactase
(~20%) are unable to digest lactose and
have the condition called lactose
intolerance.
17-29
Disaccharides: Maltose
Maltose is formed by linking two -D-glucose
molecules to give a 1,4 glycosidic link.
CH2OH
CH2OH
O
O
H
H
H
H
H
H
OH
H
OH H
O
OH
HO
H
OH
H
OH
Maltose is malt sugar. It is formed when
starch is partly hydrolyzed. It is a reducing
sugar due to the free acetal.
17-30
Disaccharides:Cellobiose
Cellobiose is formed by linking two  Dglucose molecules to give a 1,4 glycosidic
link. It comes from hydrolyzed cellulose.
CH2OH
CH2OH

O
O
H

H
OH
H
H
O
OH H
OH H
H
HO
H
H
OH
H
OH
17-31
17.6 Polysaccharides: Cellulose
Cellulose is the major structural polymer
in plants. It is a liner homopolymer
composed of -D-glucose units linked
-1,4. The repeating disaccharide of
cellulose is -cellobiose.
Animals lack the enzymes necessary to
hydrolyze cellulose. The bacteria in
ruminants (eg. cows) can digest
cellulose so that they can eat grass,
etc.
17-32
Structure of Cellulose
-(1->4) glycosidic bond
CH2OH
O
H
O
CH2OH
H
OH
H
CH2OH
O
H
H
O
H
O
H
H
OH
OH
H
O
H
H
OH H
H
H
OH
O
H
OH
17-33
Polysaccharides: Starch
Starches are storage forms of glucose
found in plants.
They are polymers of  linked glucose.
If the links are only 1,4, the polymer is
linear and is called amylose. (Figure
on next slide.) Amylose usually
assumes a helical configuration with
six glucose units per turn.
If the links are both 1,4 and 1,6, the
polymer is branched and is called
amylopectin. (Figure on next slide. 17-34
Polysaccharides: amylose/amylopectin
CH2 OH
CH2 OH
CH2 OH
CH2 OH
O H H
O H H
O H H
O H
H
H
H
H
H
( OH
H
OH H
OH H
OH H
O
O
O
O
O)
H OH
H OH
H OH
H OH
amylose(-1,4 links)
CH2 OH
O H
H
H
( OH
H
O
O
H OH
CH2 OH
O H H
H
H
( OH
H
O
O
H OH
CH2 OH
O H
H
H
OH H
O
amylopectin
(-1,6 link)
H OH
CH2
CH2 OH
CH2 OH
O H H
O H H
O H
H
H
H
OH H
OH H
OH H
O
O
O)
H OH
H OH
H OH 17-35
Polysaccharides: glycogen
The storage carbohydrate in animals is
glycogen. It is a branched chain
polymer like amylopectin but it has
more frequent branching (about every
10 residues). Glycogen is stored in
liver and muscle cells.
17-36
Glycoproteins
These materials contain carbohydrate
residues on protein chains. Very
important examples of these materials
are antibodies-chemicals which bind to
antigens and immobilize them.
The carbohydrate part of the
glycoprotein plays a role in
determining the part of the antigen
molecule to which the antibody binds.
17-37
Glycoproteins: 2
The human blood groups A, B, AB, and O
depend on the oligosaccharide part of
the glycoprotein on the surface of
erythrocyte cells. The terminal
monosaccharide of the glycoprotein at
the nonreducing end determines blood
group.
17-38
Glycoproteins: 3
Type
A
Terminal sugar
N-acetylgalactosamine
B
-D-galactose
AB
both the above
O
neither of the above
O is the “universal donor”
AB is the “universal acceptor”
17-39
The End
Carbohydrates
17-40