Chapter 7 Carbohydrates and Glycobiology
Multiple Choice Questions
1. Monosaccharides and disaccharides
To possess optical activity, a compound must be:
A) a carbohydrate.
B) a hexose.
C) asymmetric.
D) colored.
E) D-glucose.
2. Monosaccharides and disaccharides
Which of the following monosaccharides is not an aldose?
A) Erythrose
B) Fructose
C) Glucose
D) Glyceraldehyde
E) Ribose
3. Monosaccharides and disaccharides
The reference compound for naming D and L isomers of sugars is:
A) fructose.
B) glucose.
C) glyceraldehyde.
D) ribose.
E) sucrose.
4. Monosaccharides and disaccharides
When two carbohydrates are epimers:
A) one is a pyranose, the other a furanose.
B) one is an aldose, the other a ketose.
C) they differ in length by one carbon.
D) they differ only in the configuration around one carbon atom.
E) they rotate plane-polarized light in the same direction.
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5. Monosaccharides and disaccharides
Which of the following is an epimeric pair?
A) D-glucose and D-glucosamine
B) D-glucose and D-mannose
C) D-glucose and L-glucose
D) D-lactose and D-sucrose
E) L-mannose and L-fructose
6. Monosaccharides and disaccharides
Which of following is an anomeric pair?
A) D-glucose and D-fructose
B) D-glucose and L-fructose
C) D-glucose and L-glucose
D) –D-glucose and –D-glucose
E) –D-glucose and –L-glucose
7. Monosaccharides and disaccharides
When the linear form of glucose cyclizes, the product is a(n):
A) anhydride.
B) glycoside.
C) hemiacetal.
D) lactone.
E) oligosaccharide.
8. Monosaccharides and disaccharides
Which of the following pairs is interconverted in the process of mutarotation?
A) D-glucose and D-fructose
B) D-glucose and D-galactose
C) D-glucose and D-glucosamine
D) D-glucose and L-glucose
E) –D-glucose and –D-glucose
9. Monosaccharides and disaccharides
Which of the following is not a reducing sugar?
A) Fructose
B) Glucose
C) Glyceraldehyde
D) Ribose
E) Sucrose
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10. Monosaccharides and disaccharides
Which of the following monosaccharides is not a carboxylic acid?
A) 6-Phospho-gluconate
B) Gluconate
C) Glucose
D) Glucuronate
E) Muramic acid
11. Monosaccharides and disaccharides
D-Glucose is called a reducing sugar because it undergoes an oxidation-reduction reaction at the
anomeric carbon. One of the products of this reaction is:
A) D-galactose.
B) D-gluconate.
C) D-glucuronate.
D) D-ribose.
E) muramic acid.
12. Monosaccharides and disaccharides
Hemoglobin glycation is a process where is attached to hemoglobin.
A) glycerol; covalently
B) glucose; enzymatically
C) glucose; non-enzymatically
D) N-acetyl-galactosamine; enzymatically
E) galactose; non-enzymatically
13. Monosaccharides and disaccharides
When forming the disaccharide maltose from two glucose monosaccharides:
A) water is eliminated.
B) a hemiacetal is converted to an acetal.
C) the resulting dissacharide is no longer a reducing sugar.
D) Both A and B
E) A, B, and C above
14. Monosaccharides and disaccharides
From the abbreviated name of the compound Gal(1 → 4)Glc, we know that:
A) C-4 of glucose is joined to C-1 of galactose by a glycosidic bond.
B) the compound is a D-enantiomer.
C) the galactose residue is at the reducing end.
D) the glucose is in its pyranose form.
E) the glucose residue is the anomer.
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15. Polysaccharides
Starch and glycogen are both polymers of:
A) fructose.
B) glucose1-phosphate.
C) sucrose.
D) –D-glucose.
E) –D-glucose.
16. Polysaccharides
Which of the following statements about starch and glycogen is false?
A) Amylose is unbranched; amylopectin and glycogen contain many (1 → 6) branches.
B) Both are homopolymers of glucose.
C) Both serve primarily as structural elements in cell walls.
D) Both starch and glycogen are stored intracellularly as insoluble granules.
E) Glycogen is more extensively branched than starch.
17. Polysaccharides
Which of the following statements about hydrogen bonding in glycogen and cellulose is true?
A) Glycogen forms more internal H-bonds than cellulose.
B) Extensive internal hydrogen bonding makes cellulose more water soluble than glycogen.
C) Extensive hydrogen bonding with water makes cellulose more soluble than glycogen.
D) Glycogen primarily forms hydrogen bonds within a single chain.
E) The hydrogen bonding in cellulose favors a helical conformation.
18. Polysaccharides
Following complete hydrolysis of a sample of glycogen and a sample of cellulose, which of the
following must be true?
A) The glycogen sample is more soluble than the cellulose sample.
B) The cellulose sample is more soluble than the glycogen sample.
C) Both samples consist of a mixture of –D-glucose and –D-glucose.
D) The glycogen sample has a higher ratio of –D-glucose than the cellulose sample.
E) The cellulose sample contains only –D-glucose.
19. Polysaccharides
Which of the following is a heteropolysaccharide?
A) Cellulose
B) Chitin
C) Glycogen
D) Hyaluronate
E) Starch
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20. Glycoconjugates: proteoglycans, glycoproteins, and glycolipids
The basic structure of a proteoglycan consists of a core protein and a:
A) glycolipid.
B) glycosaminoglycan.
C) lectin.
D) lipopolysaccharide.
E) peptidoglycan.
21. Glycoconjugates: proteoglycans, glycoproteins, and glycolipids
Which of the following statements about heparan sulfate is not true?
A) Sulfation of heparan sulfate to form NS domains is important for its role as an anti-coagulant.
B) Heparan sulfate can promote protein-protein interactions via the NS domains.
C) The secondary structure of heparan sulfate is completely random.
D) The NA domains of heparan sulfate contain no sulfation.
E) The core repeating structure of heparan sulfate is made up of alternating GlcNAc and GlcA.
22. Glycoconjugates: proteoglycans, glycoproteins, and glycolipids
In glycoproteins, the carbohydrate moiety is always attached through the amino acid residues:
A) asparagine, serine, or threonine.
B) aspartate or glutamate.
C) glutamine or arginine.
D) glycine, alanine, or aspartate.
E) tryptophan, aspartate, or cysteine.
23. Glycoconjugates: proteoglycans, glycoproteins, and glycolipids
Which of the following is a dominant feature of the outer membrane of the cell wall of gram negative
bacteria?
A) Amylose
B) Cellulose
C) Glycoproteins
D) Lipopolysaccharides
E) Lipoproteins
24. Carbohydrates as informational molecules: the sugar code
The biochemical property of lectins that is the basis for most of their biological effects is their ability
to bind to:
A) amphipathic molecules.
B) hydrophobic molecules.
C) specific lipids.
D) specific oligosaccharides.
E) specific peptides.
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25. Carbohydrates as informational molecules: the sugar code
Which of the following statements concerning sialic acid residues on glycoproteins is true?
A) Sialic residues on erythrocytes are recognized by lectins, leading to removal of the erythrocytes.
B) Sialic residues on ceruloplasmin are recognized by lectins, leading to removal of ceruloplasmin.
C) Sialic residues are removed by neuraminidases.
D) The anti-viral drug oseltamavir accelerates the removal of sialic acid residues.
E) Both A and B above
26. Carbohydrates as informational molecules: the sugar code
Why is it surprising that the side chains of tryptophan residues in lectins can interact with sugars?
A) Because the side chain of tryptophan is hydrophilic and sugars are hydrophobic
B) Because the side chain of tryptophan is (–) charged and sugars are generally (+) charged or
neutral
C) Because the side chain of tryptophan can make hydrogen bonds and sugars cannot.
D) Because the side chain of tryptophan is hydrophobic and sugars are generally hydrophilic
E) None of the above
27. Working with carbohydrates
Which of the following is not a reason that it is difficult to study oligosaccharide composition from
biological systems?
A) Oligosaccharides are often branched.
B) Oligosaccharides often have a high negative charge density.
C) Oligosaccharides have a variety of linkages (e.g., 1→6 or 1→4).
D) Oligosaccharides have too much conformational flexibility.
E) There are no specific glycosidase enzymes that can be used to selectively digest oligosaccharides.
28. Working with carbohydrates
Which of the following techniques is not commonly used to study oligosaccharide structures?
A) X-ray crystallography
B) Matrix-assisted laser desorption/ionization mass spectroscopy (MALDI–MS)
C) Nuclear magnetic resonance (NMR)
D) Complete chemical synthesis
E) Oligosaccharide microarrays
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Short Answer Questions
29. Monosaccharides and disaccharides
Pages: 244–246 Difficulty: 1
Explain why all mono- and disaccharides are soluble in water.
30. Monosaccharides and disaccharides
Pages: 244–245 Difficulty: 2
This compound is L-glyceraldehyde. Draw a stereochemically correct representation of C-1 and C-2
of D-glucose.
CHO
|
HO—C—H
|
CH2OH
31. Monosaccharides and disaccharides
Pages: 244–245 Difficulty: 2
Categorize each of the following as an aldose, a ketose, or neither.
H
C
C
C
H
OH
O
H
OHH
H
C
C
C
H
OH
H
H
HO
HHO
H
C
C
C
H
OH
O
H
HHO
H
C
C
C
H
H
OH
HO
H
O
H
C
C
C
H
O
OHH
HH
(a) (b) (c) (d) (e)
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32. Monosaccharides and disaccharides
Pages: 244–248 Difficulty: 2
Define each in 20 words or fewer:
(a) anomeric carbon
(b) enantiomers
(c) furanose
(d) pyranose
(e) glycoside
(f) epimers
(g) aldose
(h) ketose
33. Monosaccharides and disaccharides
Pages: 244–256 Difficulty: 3
(a) Draw the structures of both anomers of glucose in the pyranose ring form. (b) How many
asymmetric carbons (chiral centers) does each of these structures have? (c) How many stereoisomers
of the glucose are theoretically possible?
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34. Monosaccharides and disaccharides
Pages: 244–248 Difficulty: 3
Identify all the epimeric pairs in the structures shown below.
35. Monosaccharides and disaccharides
Pages: 252–253 Difficulty: 2
In the following structure:
(a) How many of the monosaccharide units are furanoses and how may are pyranoses? (b) What is
the linkage between the two monosaccharide units? (c) Is this a reducing sugar?
Explain.
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36. Monosaccharides and disaccharides
Pages: 251 Difficulty: 2
In measuring long-term glucose levels in the bloodstream, glycated hemoglobin must be separated
from unmodified hemoglobin to determine the percentage of glycated hemoglobin. Suggest a simple
chromatographic method by which this separation can be performed.
37. Monosaccharides and disaccharides
Pages: 250–251 Difficulty: 3
(a) Define “reducing sugar.” (b) Show the reaction product of glucose after it is used as a reducing
sugar. (c) Explain why fructose is also considered a reducing sugar. (Hint: It must first undergo a
chemical conversion.) (d) Sucrose is a disaccharide composed of glucose and fructose
(Glc(1 → 2)Fru). Explain why sucrose is not a reducing sugar, even though both glucose and
fructose are.
38. Polysaccharides
Pages: 254–262 Difficulty: 2
Match these molecules with their biological roles.
(a) glycogen __ viscosity, lubrication of extracellular secretions
(b) starch __ carbohydrate storage in plants
(c) trehalose __ transport/storage in insects
(d) chitin __ exoskeleton of insects
(e) cellulose __ structural component of bacterial cell wall
(f) peptidoglycan __ structural component of plant cell walls
(g) hyaluronate __ extracellular matrix of animal tissues
(h) proteoglycan __ carbohydrate storage in animal liver
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39. Polysaccharides
Pages: 254–262 Difficulty: 2
The number of structurally different polysaccharides that can be made with 20 different
monosaccharides is far greater than the number of different polypeptides that can be made with 20
different amino acids if both polymers contain an equal number (say 100) of total residues. Explain
why.
40. Polysaccharides
Pages: 256–257 Difficulty: 2
Describe one biological advantage of storing glucose units in branched polymers (glycogen,
amylopectin) rather than in linear polymers.
41. Polysaccharides
Page: 256 Difficulty: 2
Explain how it is possible that a polysaccharide molecule, such as glycogen, may have only one
reducing end, and yet have many nonreducing ends.
42. Polysaccharides
Page: 256 Difficulty: 2
What is the biological advantage to an organism that stores its carbohydrate reserves as starch or
glycogen rather than as an equivalent amount of free glucose?
43. Polysaccharides
Pages: 256–257 Difficulty: 3
Draw the structure of the repeating basic unit of (a) amylose and (b) cellulose.
44. Polysaccharides
Page: 257 Difficulty: 2
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Explain in molecular terms why humans cannot use cellulose as a nutrient, but goats and cattle can.
45. Polysaccharides
Pages: 260–261 Difficulty: 2
The glycosaminoglycans are negatively charged at neutral pH. What components of these polymers
confer the negative charge?
46. Glycoconjugates: proteoglycans, glycoproteins, and glycolipids
Page: 253 Difficulty: 3
Sketch the principal components of a typical proteoglycan, showing their relationships and
connections to one another.
47. Glycoconjugates: proteoglycans, glycoproteins, and glycolipids
Pages: 252–253 Difficulty: 3
Describe the differences between a proteoglycan and a glycoprotein.
48. Glycoconjugates: proteoglycans, glycoproteins, and glycolipids
Pages: 253–254 Difficulty: 2
Describe the structure of a proteoglycan aggregate such as is found in the extracellular matrix.
49. Glycoconjugates: proteoglycans, glycoproteins, and glycolipids
Pages: 263–270 Difficulty: 2
How do oligosaccharide portions of glycoproteins change the properties of the proteins?
50. Carbohydrates as informational molecules: the sugar code
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Pages: 269–270 Difficulty: 3
Describe the process by which “old” serum glycoproteins are removed from the mammalian
circulatory system.
51. Carbohydrates as informational molecules: the sugar code
Pages: 269–270 Difficulty: 2
What are lectins? What are some biological processes that involve lectins?
52. Carbohydrates as informational molecules: the sugar code
Pages: 270–271 Difficulty: 2
Briefly explain how the drugs Tamiflu and Relenza work to prevent the flu.
53. Working with carbohydrates
Pages: 274–275 Difficulty: 2
Briefly explain the procedure involved in using an oligosaccharide microarray to identify the binding
specificity for a potential lectin.