644
Chapter 18
Carbohydrates
Enantiomers have identical achiral properties but different
chiral properties. Diastereomers have structures that are not
mirror images of each other (Section 18.5).
Fischer projection formulas. Fischer projection formulas are
two-dimensional structural formulas used to depict the threedimensional shapes of molecules with chiral centers (Section 18.6).
Chirality of monosaccharides. Monosaccharides are classified
as D or L stereoisomers on the basis of the configuration of the
chiral center farthest from the carbonyl group (Section 18.6).
Optical activity. Chiral compounds are optically active—that
is, they rotate the plane of polarized light. Enantiomers rotate
the plane of polarized light in opposite directions. The prefix
(1) indicates that the compound rotates the plane of polarized
light in a clockwise direction, whereas compounds that rotate
the plane of polarized light in a counterclockwise direction
have the prefix (2) (Section 18.7).
Classification of monosaccharides. Monosaccharides are classified as aldoses or ketoses on the basis of the type of carbonyl
group present. They are further classified as trioses, tetroses,
pentoses, etc. on the basis of the number of carbon atoms
present (Section 18.8).
Important monosaccharides. Important monosaccharides
include glucose, galactose, fructose, and ribose. Glucose and
galactose are aldohexoses, fructose is a ketohexose, and ribose
is an aldopentose (Section 18.9).
Cyclic monosaccharides. Cyclic monosaccharides form through
an intramolecular reaction between the carbonyl group and an
alcohol group of an open-chain monosaccharide. These cyclic
forms predominate in solution (Section 18.10).
Haworth projection formulas. Haworth projection formulas are
two-dimensional structural representations used to depict the
three-dimensional structure of a cyclic form of a monosaccharide (Section 18.11).
Reactions of monosaccharides. Five important reactions of
monosaccharides are (1) oxidation to an acidic sugar (2) reduction to a sugar alcohol (3) glycoside formation (4) phosphate
ester formation and (5) amino sugar formation (Section 18.12).
Disaccharides. Disaccharides are glycosides formed from the
linkage of two monosaccharides. The most important disaccharides are maltose, cellobiose, lactose, and sucrose. Each of these
has at least one glucose unit in its structure (Section 18.13).
Oligosaccharides. Oligosaccharides are carbohydrates that
contain three to ten monosaccharide units covalently bonded to
each other. Two important naturally occurring oligosaccharides
are raffinose and stachyose (Section 18.14).
Polysaccharides. Polysaccharides are polymers in which monosaccharides are the monomers. In homopolysaccharides, only
one type of monomer is present. Two or more monosaccharide
monomers are present in heteropolysaccharides. Storage polysaccharides (starch, glycogen) are storage molecules for monosaccharides. Structural polysaccharides (cellulose, chitin) serve
as structural elements in plant cell walls and animal
exoskeletons (Sections 18.15 to 18.18).
Glycolipids and glycoproteins. Glycolipids and glycoproteins
are molecules in which oligosaccharides are attached through
glycosidic linkages to lipids and proteins, respectively. Such
molecules often govern how cells of differing function interact
with each other (Section 18.20).
Exercises and Problems
Interactive versions of these problems may be assigned in OWL.
Exercises and problems are arranged in matched pairs with the
two members of a pair addressing the same concept(s). The answer to the odd-numbered member of a pair is given at the back
of the book. Problems denoted with a ▲ involve concepts found
not only in the section under consideration but also concepts
found in one or more earlier sections of the chapter. Problems denoted with a ● cover concepts found in a Chemical Connections
feature box.
18.6
What role does chlorophyll play in photosynthesis?
18.7
What are the two major functions of carbohydrates in
the plant kingdom?
What are the six major functions of carbohydrates in
the human body?
18.8
Classification of Carbohydrates (Section 18.3)
18.9
Define the term carbohydrate.
18.10 What functional group is present in all carbohydrates?
18.11 Indicate how many monosaccharide units are present in
Biochemical Substances (Section 18.1)
18.1
18.2
18.3
18.4
Define each of the following terms.
a. Biochemistry
b. Biochemical substance
Contrast the relative amounts, by mass, of bioorganic
and bioinorganic substances present in the human body.
What are the four major types of bioorganic substances?
For each of the following pairs of bioorganic substances,
indicate which member of the pair is more abundant in
the human body.
a. Proteins and nucleic acids
b. Proteins and carbohydrates
c. Lipids and carbohydrates
d. Lipids and nucleic acids
Occurrence of Carbohydrates (Section 18.2)
18.5
Write a general chemical equation for photosynthesis.
each of the following.
a. Disaccharide
b. Tetrasaccharide
c. Oligosaccharide
d. Polysaccharide
18.12 Identify, in general terms, the product produced from
the complete hydrolysis of each of the following types of
carbohydrates.
a. Disaccharide
b. Tetrasaccharide
c. Oligosaccharide
d. Polysaccharide
Chirality (Section 18.4)
18.13 Explain what the term superimposable means.
18.14 Explain what the term nonsuperimposable means.
Exercises and Problems
18.15
18.16
18.17
In each of the following lists of objects, identify those
objects that are chiral.
a. Nail, hammer, screwdriver, drill bit
b. Your hand, your foot, your ear, your nose
c. The words TOT, TOOT, POP, PEEP
In each of the following lists of objects, identify those
objects that are chiral.
a. Baseball cap, glove, shoe, scarf
b. Pliers, scissors, spoon, fork
c. The words MOM, DAD, AHA, WAX
Indicate whether the circled carbon atom in each of the
following molecules is a chiral center.
a. CH3 OC H2 OOH
c. CH3 O C H O OH
A
Cl
18.18
Indicate whether the circled carbon atom in each of the
following molecules is a chiral center.
a. CH3 O C H2 O NH2
c. CH3 O C H O NH2
A
CH3
18.19
b. CH3 O C H O OH
A
CH3
d. CH3 O CH2 O C H O OH
A
CH3
b. CH3 O C H O CH3
A
NH2
d. CH3 O C H O NH2
A
Cl
Use asterisks to show the chiral center(s), if any, in the
following structures.
a.
b.
H Cl H
H Cl
A A A
A A
Br O C O COC O Cl
ClO C O C O Br
A A A
A A
H Br Br
H Cl
18.22
18.20
18.21
Cl
c.
OH
d.
OH
d.
Cl
CH3
CH3
18.23
18.24
Classify each of the molecules in Problem 18.19 as
chiral or achiral.
Classify each of the molecules in Problem 18.20 as
chiral or achiral.
The alkane of lowest molecular mass that has a chiral
center has the molecular formula C7H16. Identify the
“groups” attached to the chiral center in a molecule of
this compound.
▲18.26 The saturated alcohol of lowest molecular mass that
has a chiral center has the molecular formula C4H10O.
Identify the “groups” attached to the chiral center in a
molecule of this compound.
▲18.25
Stereoisomerism: Enantiomers and Diastereomers
(Section 18.5)
18.27
18.28
18.29
18.31
How many chiral centers are present in each of the following molecular structures?
a.
b. Cl
Cl
Cl
CH3
c.
18.30
Use asterisks to show the chiral center(s), if any, in the
following structures.
H H H
a.
b.
Br Cl
A A A
A A
Cl O C O COC O Cl
ClO C O C O Cl
A A A
A A
Br OH Br
Br Br
O
c.
B
CH3O CH OCH O CH OC O H
A
A
A
OH OH OH
d. CH2O CH OCH O CH O CH2
A
A
A
A
A
OH OH OH OH OH
How many chiral centers are present in each of the following molecular structures?
Cl
a.
b.
OH
Br
c.
O
B
CH2O CH OCH O CH OC O H
A
A
A
A
OH OH OH OH
d. CH2O CH OCH O CH OCH OCH2
A
A
A
A
A
A
OH OH OH OH OH OH
645
18.32
What is the difference between constitutional isomers
and stereoisomers?
Both enantiomers and diastereomers are stereoisomers.
How do they differ?
What are two major structural features that can generate stereoisomerism?
Explain why cis–trans isomers are diastereomers rather
than enantiomers.
Indicate whether each of the following statements about
stereoisomers is true or false.
a. Stereoisomers always have the same molecular formula.
b. Stereoisomers always have the same structural formula.
c. Stereoisomers are always nonsuperimposable mirror
images of each other.
d. Stereoisomers always possess handedness.
Indicate whether each of the following statements about
enantiomers is true or false.
a. Enantiomers always have the same molecular formula.
b. Enantiomers always have the same structural formula.
c. Enantiomers are always nonsuperimposable mirror
images of each other.
d. Enantiomers always differ in handedness.
Fischer Projection Formulas (Section 18.6)
18.33
Draw the Fischer projection formula for each of the following molecules.
H
CH3
a.
b.
)C Br
Cl
CH3
c.
CH3
)C Br
H
Cl
)C Br
Cl
H
d.
CH3
H
)C Br
Cl
646
Chapter 18
18.34
Carbohydrates
Draw the Fischer projection formula for each of the following molecules.
Cl
a.
OH
c.
)CCH3
Cl
H
CH3
d.
)C Cl
HO
H
18.35
c.
18.37
18.38
18.39
H
)C OH
Cl
Draw a Fischer projection formula for the enantiomer
of each of the following monosaccharides.
a.
18.36
H
OH
b.
)C CH3
H
CH3
CHO
A
A OH
A
HO A H
CH2OH
c.
CHO
A
H A OH
A
HO A H
A
H A OH
A
HO A H
CH2OH
d.
CH2OH
A
C PO
A
HO A H
A
HO A H
CH2OH
b.
b.
CHO
A
HO A H
A
H A OH
A
H A OH
CH2OH
d.
CHO
A
H A OH
A
H A OH
A
H A OH
A
HO A H
CH2OH
CH2OH
A
C PO
A
H A OH
A
HO A H
A
H A OH
CH2OH
CHO
A
HO A H
A
HO A H
A
HO A H
CH2OH
c.
CHO
A
HO A H
A
HO A H
A
H A OH
A
H A OH
CH2OH
18.41
Indicate whether or not each of the pairs of compounds
in Problem 18.39 are epimers.
Indicate whether or not each of the pairs of compounds
in Problem 18.40 are epimers.
CH2OH
A
C PO
A
HO A H
A
HO A H
CH2OH
CH2OH
d.
A
C PO
A
H A OH
A
H A OH
A
HO A H
CH2OH
b.
Characterize the members of each of the following pairs
of structures as (1) enantiomers (2) diastereomers or
(3) neither enantiomers nor diastereomers.
a.
CHO
A
H A OH
A
HO A H
A
H A OH
CH2OH
and
CHO
A
H A OH
A
H A OH
A
H A OH
CH2OH
and
Characterize the members of each of the following pairs
of structures as (1) enantiomers (2) diastereomers or
(3) neither enantiomers nor diastereomers.
CHO
CHO
a.
A
A
H A OH
HO A H
A
and HO A H
H A OH
A
A
A
HO A H
H A OH
CH2OH
CH2OH
CHO
CHO
b.
A
A
H A OH
H A OH
A
and HO A H
H A OH
A
CH2OH
CH2OH
CHO
CHO
c.
A
A
H A OH
HO A H
A
A
HO A H
H A OH
and
A
A
H A OH
H A OH
A
A
H A OH
HO A H
CH2OH
CH2OH
d.
CH2OH
CH2OH
A
A
CPO
CPO
and
A
A
H A OH
H A CH3
A
A
H A OH
H A OH
CH2OH
CH2OH
CHO
A
H A OH
A
HO A H
A
H A OH
A
HO A H
CH2OH
Classify each of the molecules in Problem 18.35 as a
D enantiomer or an L enantiomer.
Classify each of the molecules in Problem 18.36 as a
D enantiomer or an L enantiomer.
and
18.40
Draw a Fischer projection formula for the enantiomer
of each of the following monosaccharides.
a.
and
CHO
A
H A CH3
A
HO A H
CH2OH
CHO
A
HO A H
A
H A OH
A
HO A H
A
H A OH
CH2OH
CH2OH
A
C PO
A
HO A H
A
H A OH
CH2OH
18.42
How many chiral centers are present in each of the compounds in Problem 18.39?
▲18.44 How many chiral centers are present in each of the compounds in Problem 18.40?
▲18.43
Properties of Enantiomers (Section 18.7)
18.45
D-glucose and L-glucose would be expected to show dif-
ferences in which of the following properties?
Exercises and Problems
18.46
18.47
18.48
▲18.49
a. Solubility in an achiral solvent
b. Density
c. Melting point
d. Effect on plane-polarized light
D-glucose and L-glucose would be expected to show differences in which of the following properties?
a. Solubility in a chiral solvent
b. Freezing point
c. Reaction with ethanol
d. Reaction with (1)-lactic acid
Compare (1)-lactic acid and (2)-lactic acid with respect
to each of the following properties.
a. Boiling point
b. Optical activity
c. Solubility in water
d. Reaction with (1)-2,3-butanediol
Compare (1)-glyceraldehyde and (2)-glyceraldehyde
with respect to each of the following properties.
a. Freezing point
b. Rotation of plane-polarized light
c. Reaction with ethanol
d. Reaction with (2)-2,3-butanediol
C
Cl
b. H
C
c. CH2 P CH
CH3
d. CH2
OH
CH2
18.54
18.56
b.
CH2OH
A
CP O
A
HO O C O H
A
HO O C O H
A
CH2OH
d.
CH2OH
A
CP O
A
HOO C O H
A
HO O C O H
A
H O C O OH
A
CH2OH
Classify each monosaccharide in Problem 18.51 by its
number of carbon atoms and its type of carbonyl group.
Classify each monosaccharide in Problem 18.52 by its
number of carbon atoms and its type of carbonyl group.
Using the information in Figures 18.14 and 18.15, assign
a name to each of the monosaccharides in Problem 18.51.
Using the information in Figures 18.14 and 18.15, assign
a name to each of the monosaccharides in Problem 18.52.
How many chiral centers are present in the structure of
each of the monosaccharides in Problem 18.51?
▲18.58 How many chiral centers are present in the structure of
each of the monosaccharides in Problem 18.52?
▲18.57
CH2OH
F
18.53
18.55
Indicate whether or not each of the following compounds is optically active.
CHO
H
a. Cl
CHO
A
HO O C O H
A
HO O C O H
A
HO O C O H
A
H O C O OH
A
CH2OH
c.
CHO
A
HO O C O H
A
H O C O OH
A
CH2OH
a.
647
CH2
CH3
OH
▲18.50
Indicate whether or not each of the following compounds is optically active.
CHO
H
a. Cl
C
Cl
b. H
18.59
OH
COOH
F
c. CH2 P CH2
C
Biochemically Important Monosaccharides (Section 18.9)
d. CH3
CH
CH2
CH3
18.60
OH
Classification of Monosaccharides (Section 18.8)
18.51
Classify each of the following monosaccharides as an
aldose or a ketose.
CHO
b.
a.
CH2OH
A
A
H O C O OH
CP O
A
A
H O C O OH
HO O C O H
A
A
H O C O OH
HO O C O H
A
A
H O CO OH
H O C O OH
A
A
CH2OH
CH2OH
c. CH2OH
A
CP O
A
CH2OH
18.52
d.
CH2OH
A
CP O
A
HO O C O H
A
CH2OH
Classify each of the following monosaccharides as an
aldose or a ketose.
18.61
18.62
Indicate at what carbon atom(s) the structures of each
of the following pairs of monosaccharides differ.
a. D-Glucose and D-galactose
b. D-Glucose and D-fructose
c. D-Glyceraldehyde and dihydroxyacetone
d. D-Ribose and 2-deoxy-D-ribose
Indicate whether the members of each of the following pairs of monosaccharides have the same molecular
formula.
a. D-Glucose and D-galactose
b. D-Glucose and D-fructose
c. D-Glyceraldehyde and dihydroxyacetone
d. D-Ribose and 2-deoxy-D-ribose
Indicate which of the terms aldoses, ketoses, hexoses,
and aldohexoses apply to both members of each of the
following pairs of monosaccharides. More than one
term may apply in a given situation.
a. D-Glucose and D-galactose
b. D-Glucose and D-fructose
c. D-Galactose and D-fructose
d. D-Glyceraldehyde and D-ribose
Indicate which of the terms aldoses, ketoses, trioses, and
aldohexoses apply to both members of each of the following pairs of monosaccharides. More than one term
may apply in a given situation.
a. D-Glucose and D-ribose
b. D-Fructose and dihydroxyacetone
c. D-Glyceraldehyde and dihydroxyacetone
d. D-Galactose and D-ribose
648
Chapter 18
18.63
18.64
18.65
18.66
Carbohydrates
Draw the Fischer projection formula for each of the
following monosaccharides.
b. D-Glyceraldehyde
a. D-Glucose
c. D-Fructose
d. L-Galactose
Draw the Fischer projection formula for each of the
following monosaccharides.
b. D-Ribose
a. D-Galactose
c. Dihydroxyacetone
d. L-Glucose
To which of the common monosaccharides does each of
the following terms apply?
a. Levulose
b. Grape sugar
c. Brain sugar
To which of the common monosaccharides does each of
the following terms apply?
a. Dextrose
b. Fruit sugar
c. Blood sugar
18.75
18.76
18.77
18.78
18.68
18.69
18.70
18.71
18.72
Indicate whether each of the following types of monosaccharides, upon intramolecular cyclization, forms
a six-membered ring, a five-membered ring, or a
four-membered ring.
a. Aldohexose
b. Ketohexose
c. Aldopentose
d. Ketopentose
Identify the two carbon atoms, using numbers (C1, C2,
C3, etc.), that bear the functional groups that interact
during the intramolecular cyclization of each of the
following types of monosaccharides.
a. Aldohexose
b. Aldopentose
c. Ketohexose
d. Ketopentose
18.79
Draw Haworth projection formulas for the a-anomer
of monosaccharides with each of the following Fischer
projection formulas.
b.
a.
CHO
CHO
A
A
H OAO OH
H OAO OH
A
A
H OO
HO OO
A OH
A H
A
A
HO OOH
H OOOH
A
A
A
A
H OAO OH
CH2OH
CH2OH
18.80
Draw Haworth projection formulas for the b-anomer
of monosaccharides with each of the following Fischer
projection formulas.
b.
a.
CHO
CHO
A
A
HO OAO H
H OAO OH
A
A
HO OO
H OO
A H
A OH
A
A
HO OOH
H OOOH
A
A
A
A
H OAO OH
CH2OH
CH2OH
18.81
Identify each of the following Haworth projection
formulas as that of an a-D-monosaccharide or a
b-D-monosaccharide.
CH2OH
CH2OH
b.
a.
O
O
HO
How many carbon atoms end up outside the ring in
the cyclization of the open-chain form of the following
monosaccharides?
b. D-Galactose
a. D-Glucose
c. D-Fructose
d. D-Ribose
After cyclization of each of the monosaccharides in
Problem 18.69, how many of the carbon atoms do not
have a hydroxyl group directly attached to it?
One of the cyclic forms of D-glucose has the structure
CH2OH
O
OH
OH
OH
OH
a. How many anomeric carbon atoms are present in this
structure?
b. How many hemiacetal carbon atoms are present in
this structure?
One of the cyclic forms of D-galactose has the structure
CH2OH
O OH
OH
OH
OH
a. How many anomeric carbon atoms are present in this
structure?
b. How many hemiacetal carbon atoms are present in
this structure?
18.73
18.74
Draw the structure for the anomer of the monosaccharide in Problem 18.71.
Draw the structure for the anomer of the monosaccharide in Problem 18.72.
The structure of D-glucose is sometimes written in an
open-chain form and sometimes in a cyclic form.
Explain why either form is acceptable.
When pure a-D-glucose is dissolved in water, both
a-D-glucose and b-D-glucose are soon present. Explain
why this is so.
Haworth Projection Formulas (Section 18.11)
Cyclic Forms of Monosaccharides (Section 18.10)
18.67
Classify the monosaccharide structure in Problem 18.71
as an a-anomer or a b-anomer.
Classify the monosaccharide structure in Problem 18.72
as an a-anomer or a b-anomer.
HO
OH
OH
OH
CH2OH
O
c.
HO
18.82
OH
OH
d. HOCH2
OH
OH
OH
O
CH2OH
OH
OH
OH
OH
Identify each of the following Haworth projection
formulas as an a-D-monosaccharide or a
b-D-monosaccharide.
CH2OH
CH2OH
b.
a.
O
O
HO
OH
HO
OH
OH
OH
OH
OH
Exercises and Problems
c.
CH2OH
O
d. HOCH2
O
CH2OH
O
a.
CH2OH
649
OH
HO
18.83
18.84
18.85
18.86
18.87
18.88
OH
OH
OH
OH
OOCH3
HO
OH
Draw the open-chain form for each of the monosaccharides in Problem 18.81.
Draw the open-chain form for each of the monosaccharides in Problem 18.82.
OH OH
CH2OH
O
b.
Using the information in Figures 18.14 and 18.15,
assign a name to each of the monosaccharides in
Problem 18.81.
Using the information in Figures 18.14 and 18.15,
assign a name to each of the monosaccharides in
Problem 18.82.
OH
HO
OH
c. HOCH2 O
18.90
18.91
18.92
18.93
18.94
18.95
18.96
18.97
Draw the Fischer projection formula for the galactose
derivative formed when galactose undergoes each of the
following changes.
a. The !CHO group is oxidized.
b. The !CH2OH group is oxidized.
c. Both the !CHO group and !CH2OH group are
oxidized.
d. The !CHO group is reduced.
Draw the Fischer projection formula for the glucose
derivative formed when glucose undergoes each of the
following changes.
a. The !CHO group is oxidized.
b. Both the !CHO group and !CH2OH group
are oxidized.
c. The !CHO group is reduced.
d. The !CH2OH group is oxidized.
OOCH2OCH3
OH
CH2OH
O
d.
OOCH3
OH
HO
OH
18.98
CH2OH
O
OOCH2OCH3
HO
OH OH
CH2OH
O
b.
OOCH3
HO
OH
OH
c. HOCH
2
O
CH2OH
OOCH2OCH3
Name each of the galactose derivatives in
Problem 18.89.
Name each of the glucose derivatives in
Problem 18.90.
Indicate whether each of the following structures is that
of a glycoside.
Indicate whether each of the following structures is that
of a glycoside.
a.
Classify each of the galactose derivatives in Problem 18.89
as an acidic sugar or a sugar alcohol.
Classify each of the glucose derivatives in Problem 18.90
as an acidic sugar or a sugar alcohol.
Which of the following monosaccharides is a reducing
sugar?
b. D-Galactose
a. D-Glucose
c. D-Fructose
d. D-Ribose
Which of the following monosaccharides will give a
positive test with Benedict’s solution?
b. D-Galactose
a. D-Glucose
c. D-Fructose
d. D-Ribose
CH2OH
OH
Draw the Haworth projection formula for each of the
following monosaccharides.
b. b-D-Galactose
a. a-D-Galactose
c. a-L-Galactose
d. b-L-Galactose
Draw the Haworth projection formula for each of the
following monosaccharides.
b. b-D-Mannose
a. a-D-Mannose
c. a-L-Mannose
d. b-L-Mannose
Reactions of Monosaccharides (Section 18.12)
18.89
OOCH2OCH3
OH
OH
CH2OH
O
d.
OOCH3
HO
OH
OH
For each structure in Problem 18.97, identify the
configuration at the acetal carbon atom as a or b.
18.100 For each structure in Problem 18.98, identify the
configuration at the acetal carbon atom as a or b.
18.99
18.101 Identify the alcohol needed to produce each of the
compounds in Problem 18.97 by reaction of the
alcohol with the appropriate monosaccharide.
18.102
Carbohydrates
Identify the alcohol needed to produce each of the
compounds in Problem 18.98 by reaction of the
alcohol with the appropriate monosaccharide.
OH
With the help of Figures 18.14 and 18.15, name each
of the compounds in Problem 18.97.
▲18.104 With the help of Figures 18.14 and 18.15, name each
of the compounds in Problem 18.98.
▲18.103
18.105
18.106
CH2OH
O
Draw structures for the following compounds.
a. a-D-Galactose-1-phosphate
b. b-D-Galactose-1-phosphate
Draw structures for the following compounds.
a. a-D-Galactose-6-phosphate
b. b-D-Galactose-6-phosphate
c.
HO
18.112
18.113
G D
O
G
O
G
CH2
OH
OH
18.114
G D
O
OH
OH
OH
OH
CH2OH
O
a.
OH
CH2OH
O
D
O
D
OH
OH
OH
OH
OH
CH2OH
O
b.
HO
OH
HO
HOCH2
O
O
OH
CH2OH
OH
CH2OH
O
c.
HO
CH2
HO
O
O
OH
HO
OH
CH2OH
O
d.
OH
OH
Indicate whether or not each of the following disaccharides contains (1) two acetal carbon atoms (2) two
hemiacetal carbon atoms or (3) one acetal and one
hemiacetal carbon atom.
O
HO
OH
OH
CH2OH
O
OH
Indicate whether or not each of the following disaccharides contains (1) two acetal carbon atoms (2) two
hemiacetal carbon atoms or (3) one acetal and one
hemiacetal carbon atom.
a.
CH2OH
O
OH
OH
OH
CH2OH
O
d.
Indicate whether or not each of the following disaccharides is a reducing sugar.
a. Sucrose
b. Maltose
c. Lactose
d. Cellobiose
Indicate whether or not each of the following disaccharides gives a positive Benedict’s test.
a. Maltose b. Cellobiose c. Sucrose d. Lactose
HO
CH2OH
O
OH
Disaccharides (Section 18.13)
18.111
OH
OH
CH2OH
O
HO
Which of the disaccharides maltose, cellobiose, lactose,
and sucrose has each of the following characteristics?
More than one disaccharide may have the indicated
characteristic.
a. Both monosaccharide units are the same.
b. An a(1 : 4) glycosidic linkage is present.
c. One of the monosaccharide components is
galactose.
d. Hydrolysis produces two different monosaccharides.
Which of the disaccharides maltose, cellobiose, lactose,
and sucrose has each of the following characteristics?
More than one disaccharide may have the indicated
characteristic.
a. Two different monosaccharide units are present.
b. A b(1 : 4) glycosidic linkage is present.
c. One of the monosaccharide components is fructose.
d. Hydrolysis produces a single substance.
OH
OH
With the help of Figure 18.14, draw structures for the
following compounds.
b. N-acetyl-a-D-gulosamine
a. a-D-gulosamine
▲18.108 With the help of Figure 18.14, draw structures for the
following compounds.
b. N-acetyl-a-D-allosamine
a. a-D-allosamine
18.110
D
O
D
OH
▲18.107
18.109
CH2OH
O
b.
D
D
Chapter 18
D
D
650
OH
OH
OH
CH2OH
O
G D
O
OH
OH
OH
OH
OH
Exercises and Problems
18.115
18.116
18.117
18.118
18.119
18.120
18.121
18.122
18.123
18.124
For each of the structures in Problem 18.113, specify
whether the disaccharide is in an a configuration or a
b configuration, or neither.
For each of the structures in Problem 18.114, specify
whether the disaccharide is in an a configuration or a
b configuration, or neither.
c. Lactase persistence is a condition in which people
cannot hydrolyze lactose in their digestive tract.
d. The level of lactase in humans varies by ethnic
group.
● 18.129
(Chemical Connections 18-B) Indicate whether each of
the following statements concerning use of sucrose and
fructose as sweeteners is true or false.
a. Fructose has a “sweetness factor” that is 7 times
greater than that of fructose.
b. HFCS-42 contains 42% sucrose.
c. The switch from sucrose to HFCS was economically
driven.
d. Oranges and grapes are the two fruits with the highest fructose/glucose ratio.
● 18.130
(Chemical Connections 18-B) Indicate whether each of
the following statements concerning use of sucrose and
fructose as sweeteners is true or false.
a. The source for HFCS is milled barley.
b. HFCS-90 is the sweetener used in the soft drink
industry.
c. The acronym HFCS stands for “high-frequency
concentrated sucrose.”
d. Most fruits have a fructose/glucose ratio between
3 and 5.
● 18.131
(Chemical Connections 18-C) Indicate whether each of
the following statements concerning sugar substitutes is
true or false.
a. Aspartame is the most widely used sugar
substitute.
b. Sucralose is a sucrose molecule in which three of
the hydroxyl groups have been replaced with methyl
groups.
c. A requirement for FDA approval of a sugar substitute is that it must be heat-stable.
d. Sodium cyclamate is no longer used as a sugar substitute because it causes cancer in animals.
● 18.132
(Chemical Connections 18-C) Indicate whether each of
the following statements concerning sugar substitutes is
true or false.
a. Aspartame is a zero-calorie sugar substitute.
b. Saccharin is a sugar substitute that is banned in
Canada but approved for use in the United States.
c. Sucralose has a sweetness factor greater than that of
other FDA-approved sugar substitutes.
d. Neotame and aspartame have structures based on
the same two amino acid building blocks.
Identify each of the structures in Problem 18.113 as a
reducing sugar or a nonreducing sugar.
Identify each of the structures in Problem 18.114 as a
reducing sugar or a nonreducing sugar.
Draw the structures of the substances produced when
each of the disaccharides in Problem 18.113 undergoes
hydrolysis.
Draw the structures of the substances produced when
each of the disaccharides in Problem 18.114 undergoes
hydrolysis.
What type of glycosidic linkage [a(1 : 4), etc.] is present in each of the disaccharides in Problem 18.113?
What type of glycosidic linkage [a(1 : 4), etc.] is present in each of the disaccharides in Problem 18.114?
Draw the structure of the disaccharide sophorose,
given that it contains an a-D-glucose unit, a b-Dglucose unit, and a b(1 : 2) glycosidic linkage.
Draw the structure of the disaccharide isomalatose,
given that it contains an a-D-glucose unit, a b-Dglucose unit, and a a(1 : 6) glycosidic linkage.
▲18.125
Indicate which of the terms monosaccharide, disaccharide, reducing sugar, anomers, enantiomers, and
aldohexose applies to both members of each of the
following pairs of substances. More than one term
may apply to a given pair of substances.
a. a-D-Glucose and b-D-glucose
b. Sucrose and maltose
c. D-Fructose and L-fructose
d. Lactose and galactose
▲18.126
Indicate which of the terms monosaccharide, disaccharide, reducing sugar, anomers, enantiomers, and
aldohexose applies to both members of each of the
following pairs of substances. More than one term
may apply to a given pair of substances.
a. a-D-Glucose and a-D-galactose
b. Sucrose and cellobiose
c. Glyceraldehyde and dihydroxyacetone
d. D-Ribose and L-ribose
(Chemical Connections 18-A) Indicate whether each
of the following statements concerning lactose, lactase,
and lactose intolerance is true or false.
a. The level of the enzyme lactase in humans decreases
with age.
b. Lactase-persistent people cannot drink milk after
childhood.
c. Lactose intolerance is lowest among Mediterranean
people.
d. Lactase is the principal carbohydrate in milk.
● 18.128 (Chemical Connections 18-A) Indicate whether each
of the following statements concerning lactose, lactase,
and lactose intolerance is true or false.
a. The enzyme lactose is required for the hydrolysis of
milk sugar.
b. Lactose-intolerant people have an allergy to the
lactose present in milk.
651
● 18.127
Oligosaccharides (Section 18.14)
18.133
Characterize the oligosaccharide raffinose in terms of
a. total number of monosaccharide units present.
b. total number of different kinds of monosaccharide
units present.
c. total number of glycosidic linkages present.
d. total number of different kinds of glycosidic linkages
present.
18.134
Characterize the oligosaccharide stachyose in terms of
a. total number of monosaccharide units present.
b. total number of different kinds of monosaccharide
units present.
c. total number of glycosidic linkages present.
d. total number of different kinds of glycosidic linkages
present.
652
Chapter 18
Carbohydrates
Indicate whether or not one or more galactose monosaccharide units is/are present in the structure of the
following carbohydrates.
a. Sucrose
b. Ribose c. Stachyose d. Lactose
▲18.136 Indicate whether or not one or more galactose monosaccharide units is/are present in the structure of the
following carbohydrates.
a. Cellobiose
b. Fructose
c. Raffinose
d. Maltose
▲18.135
Identify the type(s) of glycosidic linkage(s) [a(1 : 4),
etc.] present in each of the following carbohydrates, or
indicate that none are present.
a. Maltose
b. Galactose
c. Stachyose
d. Fructose
▲18.138 Identify the type(s) of glycosidic linkage(s) [a(1 : 4),
etc.] present in each of the following carbohydrates, or
indicate that none are present.
a. Sucrose
b. Raffinose
c. Cellobiose
d. Lactose
18.146
Indicate whether or not each of the following is a correct characterization for glycogen.
a. It is a homopolysaccharide.
b. It contains two different types of monosaccharide
molecules.
c. It is a branched-chain glucose polymer.
d. All glycosidic linkages present are a(1 : 4).
18.147
What is the difference, if any, between the amylose
and amylopectin forms of starch in terms of the
following?
a. Relative abundance
b. Length of polymer chain
c. Type of glycosidic linkages present
d. Type of monosaccharide monomers present
Which of the characterizations homopolysaccharide,
heteropolysaccharide, straight-chain polysaccharide, and
storage polysaccharide applies to both members of each
of the following pairs of substances? More than one
characterization may apply in a given situation.
a. Glycogen and starch
b. Amylose and amylopectin
c. Glycogen and amylose
d. Starch and amylopectin
▲18.137
(Chemical Connections 18-D) Indicate whether each of
the following statements concerning blood-type chemistry is true or false.
a. There are four types of oligosaccharide markers for
red blood cells.
b. The oligosaccharide marker for type O blood is a
tetrasaccharide.
c. Blood-type distribution varies by ethnic group.
d. The monosaccharide derivative N-acetylglucosamine is a component of all red blood cell biochemical markers.
● 18.140 (Chemical Connections 18-D) Indicate whether each of
the following statements concerning blood-type chemistry is true or false.
a. Oligosaccharide markers are attached to red blood
cells via a galactose monosaccharide unit.
b. The oligosaccharide marker for type A blood is a
hexasaccharide.
c. Fucose is a galactose derivative in which a !CH3
group has replaced a !CH2OH group.
d. Type B blood is more prevalent in Asian people
than in Hispanic people.
18.148
● 18.139
Structural Polysaccharides (Section 18.17)
18.149
18.150
18.151
General Characteristics of Polysaccharides
(Section 18.15)
18.141
18.142
18.143
18.144
What is the difference, if any, between a polysaccharide
and a glycan?
What is the difference, if any, between a homopolysaccharide and a heteropolysaccharide?
18.152
What is the range for the polymer chain length in a
polysaccharide?
Contrast polysaccharides with mono- and disaccharides in terms of general property differences.
Storage Polysaccharides (Section 18.16)
18.145
Indicate whether or not each of the following is a correct characterization for the amylose form of starch.
a. It is a homopolysaccharide.
b. It contains two different types of monosaccharide
molecules.
c. It is a branched-chain glucose polymer.
d. All glycosidic linkages present are a(1 : 4).
▲18.153
Indicate whether or not each of the following is a correct
characterization for cellulose.
a. It is an unbranched glucose polymer.
b. Its glycosidic linkages are of the same type as those
in starch.
c. It is a source of nutrition for humans.
d. One of its biochemical functions is that of dietary fiber.
Indicate whether or not each of the following is a correct
characterization for chitin.
a. It is an unbranched polymer.
b. Two different types of monomers are present.
c. Glycosidic linkages present are the same as those in
cellulose.
d. The monomers present are glucose derivatives rather
than glucose itself.
Indicate whether or not each of the following characterizations applies to (1) both cellulose and chitin
(2) to cellulose only (3) to chitin only or (4) to neither
cellulose nor chitin.
a. Storage polysaccharide
b. Monomers are glucose units
c. Glycosidic linkages are all a(1 : 4)
d. An unbranched polymer
Indicate whether or not each of the following characterizations applies to (1) both cellulose and chitin
(2) to cellulose only (3) to chitin only or (4) to neither
cellulose nor chitin.
a. Structural polysaccharide
b. Monomers are glucose derivatives
c. Glycosidic linkages are all (1 : 4)
d. Homopolysaccharide
Match each of the following structural characteristics
to the polysaccharides amylopectin, amylose, glycogen,
cellulose, and chitin. A specific characteristic may apply
to more than one of the polysaccharides.
a. a(1 : 4) glycosidic linkages are present.
b. All of the glycosidic linkages present are of the
same type.
Exercises and Problems
c. The polymer chain is unbranched.
d. The monosaccharide repeating unit is not glucose.
▲18.154 Match each of the following structural characteristics
to the polysaccharides amylopectin, amylose, glycogen,
cellulose, and chitin. A specific characteristic may apply
to more than one of the polysaccharides.
a. b(1 : 4) glycosidic linkages are present.
b. Two different kinds of glycosidic linkages are present.
c. The polymer chain is branched.
d. The monosaccharide repeating unit is a glucose
derivative.
Acidic Polysaccharides (Section 18.18)
18.155
18.156
Indicate whether each of the following statements about
the polysaccharide hyaluronic acid is true or false.
a. One of its monosaccharide building blocks is NAG.
b. One of its monosaccharide building blocks has a
22 charge.
c. Two types of glycosidic linkages are present.
d. One of its biochemical functions is as a lubricant for
joints.
Indicate whether each of the following statements about
the polysaccharide heparin is true or false.
a. Its biochemical function is to dissolve blood clots.
b. Both of its monosaccharide building blocks contain
the element sulfur.
c. b(1 : 3) glycosidic linkages are present.
d. It has one of the longest chain lengths of any
polysaccharide.
Which of the characterizations homopolysaccharide,
heteropolysaccharide, branched polysaccharide, and
unbranched polysaccharide applies to both members
of each of the following pairs of carbohydrates?
More than one characterization may apply in a given
situation.
a. Starch and cellulose
b. Glycogen and amylopectin
c. Amylose and chitin
d. Heparin and hyaluronic acid
▲ 18.158 Which of the characterizations homopolysaccharide,
heteropolysaccharide, branched polysaccharide, and
unbranched polysaccharide applies to both members
of each of the following pairs of carbohydrates?
More than one characterization may apply in a given
situation.
a. Glycogen and starch
b. Amylose and amylopectin
c. Chitin and hyaluronic acid
d. Heparin and cellulose
▲ 18.157
Indicate whether each of the following is a storage
polysaccharide, a structural polysaccharide, an acidic
polysaccharide, or a non-polysaccharide.
a. Amylose
b. Stachyose
c. Hyaluronic acid
d. Cellulose
▲18.160 Indicate whether each of the following is a storage
polysaccharide, a structural polysaccharide, an acidic
polysaccharide, or a non-polysaccharide.
a. Heparin b. Chitin c. Glycogen d. Raffinose
▲18.159
▲18.161
Match the polysaccharides amylopectin, amylose, cellulose, chitin, glycogen, heparin, and hyaluronic acid to the
653
following glycosidic linkage characterizations. More
than one of the polysaccharides may be correct in a
given situation.
a. All glycosidic linkages present are the same.
b. Some, but not all, glycosidic linkages are a(1 : 4)
linkages.
c. Both b(1 : 3) and b(1 : 4) glycosidic linkages are
present.
d. All glycosidic linkages are a(1 : 4) linkages.
▲18.162 Match the polysaccharides amylopectin, amylose, cellulose, chitin, glycogen, heparin, and hyaluronic acid to the
following glycosidic linkage characterizations. More
than one of the polysaccharides may be correct in a
given situation.
a. Two different types of glycosidic linkages are
present.
b. Some, but not all, glycosidic linkages are a(1 : 6)
linkages.
c. All glycosidic linkages are (1 : 4) linkages.
d. All glycosidic linkages are b(1 : 4) linkages.
Dietary Considerations and Carbohydrates
(Section 18.19)
18.163
18.164
18.165
18.166
In a dietary context, what is the difference between a
simple carbohydrate and a complex carbohydrate?
In a dietary context, what is the difference between a
natural sugar and a refined sugar?
In a dietary context, what are empty calories?
In a dietary context, what is the glycemic effect?
(Chemical Connections 18-E) Indicate whether each of
the following statements concerning glycemic response
measurement is true or false.
a. A GL value is usually 2 to 3 times larger than the
GI value for the same food.
b. The standard for GI values is usually whole-wheat
bread.
c. GI values are based on a food portion size that
contains a specific amount of carbohydrate.
d. Larger bites of food evoke a different glycemic
response than smaller bites of the same food.
● 18.168 (Chemical Connections 18-E) Indicate whether each of
the following statements concerning glycemic response
measurement is true or false.
a. A GI value is a ratio of blood-glucose change
compared to a standard.
b. Overripe fruit produces a different glycemic response
than the same fruit when it is underripe.
c. The serving-size standard for GI values is 10 g of
contained carbohydrate.
d. Some carbohydrate-containing foods have a high
GI value and a low GL value.
● 18.167
Glycolipids and Glycoproteins (Section 18.20)
18.169
18.170
In terms of general structure, what is a glycolipid?
In terms of general structure, what is a glycoprotein?
18.171
Describe the general features of the cell recognition
process in which glycoproteins participate.
Describe the general features of the cell recognition
process in which glycolipids participate.
18.172