Lecture 3 Sugars and polysaccharides Chapter 10

Question 1

(CH2O)n is the basic empirical formula for _______.

Answer 1

carbohydrates

Question 2

What are the smallest carbohydrates? Select all that apply.
a. aldose
b. altrose
c. dihydroxyacetone
d. ketose
e. triose

Answer 2

c. dihydroxyacetone/ e. triose

Question 3

. The simplest polysaccharide is:
a. monosaccharide.
b. disaccharide.
c. UDP.
d. maltose.
e. acetylglucosamine.

Answer 3

b. disaccharide.

Question 4

What is one of the sweetest chemicals known?
a. β-D-glucose
b. D-ribose
c. D-deoxyribose
d. β-D-fructopyranose
e. β-D-fructofuranose

Answer 4

d. β-D-fructopyranose

Question 5

What provides carbohydrates with an ability to form a vast array of spatial structures?
a. They function in parallel with polysaccharides.
b. They are just as amino acids are for proteins.
c. The nature of covalent bonds of monosaccharides varies highly.
d. A large variety of monosaccharides can be linked together in many different ways.
e. Monosaccharides are basically hydrates of carbon.

Answer 5

d. A large variety of monosaccharides can be linked together in many different ways.

Question 6

. A tetrose has asymmetric carbon atoms in the D and L configuration in the second and third positions, respectively. What is the respective configuration of the tetrose?
a. D
b. L
c. DL
d. α
e. β

Answer 6

b. L

Question 7

How many asymmetric carbon atoms are there in the open-chain aldoheptose molecule?
a. 4
b. 5
c. 6
d. 7
e. 8

Answer 7

b. 5

Question 8

What is the chemical basis for cyclization of monosaccharides?
a. Aldehyde can react with an alcohol to form a pyranose.
b. The hydroxyl group of the sugar can attack carbonyl groups.
c. The hydroxyl group of the monosaccharide is forced to react with its own carbonyl group due to the influence of alcohol.
d. The carbonyl carbon of the sugar can attack the hydroxyl group of the same sugar.
e. The hydroxyl group of the sugar can attack the carbonyl carbon of the same sugar.

Answer 8

c. The hydroxyl group of the monosaccharide is forced to react with its own carbonyl group due to the influence of alcohol.

Question 9

Which carbon atoms are involved in the formation of α-D-fructofuranose?
a. C-1 aldehyde group and C-5 hydroxyl group
b. C-2 aldehyde group and C-6 hydroxyl group
c. C-1 keto group and C-5 hydroxyl group
d. C-2 keto group and C-6 hydroxyl group
e. C-2 keto group and C-5 hydroxyl group

Answer 9

c. C-1 keto group and C-5 hydroxyl group

Question 10

Which carbon atoms are involved in the formation of α-D-fructopyranose?
a. C-1 aldehyde group and C-5 hydroxyl group
b. C-2 aldehyde group and C-6 hydroxyl group
c. C-1 keto group and C-5 hydroxyl group
d. C-2 keto group and C-6 hydroxyl group
e. C-2 keto group and C-5 hydroxyl group

Answer 10

d. C-2 keto group and C-6 hydroxyl group

Question 11

How many asymmetric carbon atoms are there in the β-D-glucopyranose molecule?
a. 2
b. 3
c. 4
d. 5
e. 6

Answer 11

d. 5

Question 12

Which carbon atom will always be outside of the ring in the cyclized form of the ketose?
a. C-1
b. C-2
c. C-β
d. C-5
e. C-6

Answer 12

a. C-1

Question 13

Which carbon atom of aldohexose CANNOT be a part of a pyranose ring?
a. C-1
b. C-2
c. C-β
d. C-5
e. C-6

Answer 13

c. C-β

Question 14

Which carbon atom is anomeric in the furanose form of fructose?
a. C-1
b. C-2
c. C-β
d. C-5
e. C-6

Answer 14

b. C-2

Question 15

In cyclic carbohydrates:
a. steric hindrance between hydroxyl groups of the carbohydrate makes the “boat” conformation more stable.
b. hydrogen atoms in the axial positions provide less steric hindrance since axial bonds are nearly perpendicular to the plane of the cycle.
c. equatorial bonds are nearly parallel to the plane of the cycle in the “chair” form but nearly perpendicular in the “boat” form.
d. hydrogen atoms in equatorial positions of the “boat” conformation cause more hindrance than in the “chair” conformation.
e. axial bonds provide less steric hindrance for functional groups since they are nearly perpendicular to the plane of the cycle.

Answer 15

b. hydrogen atoms in the axial positions provide less steric hindrance since axial bonds are nearly perpendicular to the plane of the cycle.

Question 16

16. Choose the WRONG statement about ketoses.
    a. The anomeric carbon exists only in the cyclic form of the monosaccharide such as fructose.
    b. The pyranose form of fructose predominates in the free solution.
    c. The C-1 keto group in the open-chain form of some ketoses can form an intramolecular hemiketal.
    d. The positioning of the keto group in the chain leaves ketoses with one fewer asymmetric center.
    e. Dihydroxyacetone is one of the smallest ketoses.

Answer 16

c. The C-1 keto group in the open-chain form of some ketoses can form an intramolecular hemiketal.

Question 17

Choose the CORRECT statement about glycoproteins.
a. About 80% of the simple glycoprotein molecule can be a carbohydrate.
b. In proteoglycans, carbohydrate components make up about 95% of the molecule by weight.
c. Half of the proteome is proteoglycans.
d. In mucins, moieties of N-acetylgalactosamine can make up about 40% of the molecule by weight.
e. Only 1%–2% of the proteome is glycosylated.

Answer 17

b. In proteoglycans, carbohydrate components make up about 95% of the molecule by weight.

Question 18

Reducing sugars are called so due to a(n):
a. ability of the cyclic form of the carbohydrate to reduce substances.
b. disability of the open-chain form of the carbohydrate to reduce cupric ions.
c. ability of the open-chain form of the carbohydrate to be oxidized.
d. ability of the cyclic form of the carbohydrate to be oxidized.
e. ability of the open-chain form of the carbohydrate to be reduced.

Answer 18

c. ability of the open-chain form of the carbohydrate to be oxidized.

Question 19

Which bonds links monosaccharides in oligosaccharides?
a. N-glycosidic bonds
b. O-glycosidic bonds
c. ester bonds
d. N-linkages
e. noncovalent interactions

Answer 19

b. O-glycosidic bonds

Question 20

What are the products of the reaction of invertase?
a. α-D-glucopyranose and β-D-glucopyranose
b. α-D-glucopyranose and β-L-fructopyranose
c. β-D-glucopyranose and α-L-galactopyranose
d. α-D-glucopyranose and β-D-fructofuranose
e. β-D-fructofuranose and α-L-glucopyranose

Answer 20

d. α-D-glucopyranose and β-D-fructofuranose

Question 21

Which disaccharide comes from the hydrolysis of starch?
a. maltase
b. sucrose
c. maltose
d. amylose
e. lactose

Answer 21

c. maltose

Question 22

What is NOT a homopolymeric polysaccharide?
a. amylose
b. amylopectin
c. glycogen
d. aggrecan
e. cellulose

Answer 22

d. aggrecan

Question 23

24. What statement about polysaccharides is TRUE?
    a. The hollow helix is formed when monosaccharides are N-linked.
    b. Soluble O-linked polysaccharides can improve absorption of nutrients.
    c. The α-1,4 linkages favor straight structures, which are more suitable for storage.
    d. Insoluble β-linked polysaccharides can improve absorption of nutrients.
    e. Pectin can increase the rate at which digestion products pass through the large intestine.

Answer 23

b. Soluble O-linked polysaccharides can improve absorption of nutrients.

Question 24

During synthesis of sucrose by a glycosyltransferase, the oxygen atom of the glycosidic bond comes from the hydroxyl group on the:
a. first carbon atom of α-D-glucopyranose since in UDP-glucose, UDP is connected to this oxygen.
b. second carbon atom of α-D-fructofuranose since in UDP-fructose, UDP is connected to this oxygen.
c. second carbon atom of β-D-fructofuranose since oxygen of α-D-glucopyranose is left as part of UDP after the transfer.
d. fifth carbon atom of β-D-fructofuranose since oxygen of α-D-glucopyranose is left as part of UDP after the transfer.
e. second carbon atom of α-D-fructofuranose since oxygen of β-D-glucopyranose is left as part of UDP after the transfer.

Answer 24

c. second carbon atom of β-D-fructofuranose since oxygen of α-D-glucopyranose is left as part of UDP after the transfer.

Question 25

26. How many nucleotides are required for a glycosyltransferase to synthesize a disaccharide? a. 1 b. 2 c. 3 d. 0 e. 1%–2% of the total nucleotides

Answer 25

a. 1

Question 26

N-linked oligosaccharides: a. don't contain N-acetylglucosamine. b. can't bind sialic acid to the pentasaccharide core. c. don't contain several mannoses. d. can't bind additional sugars to the mannose part of the pentasaccharide core. e. constitute the bigger part of glycoproteins.

Answer 26

d. can't bind additional sugars to the mannose part of the pentasaccharide core.

Question 27

In nutrient sensing, what does the acetyl group of GlcNAc indicate? a. carbohydrate availability b. fatty acid availability c. protein availability d. diabetes e. oligosaccharide structure

Answer 27

d. can't bind additional sugars to the mannose part of the pentasaccharide core.

Question 28

In nutrient sensing, what does the acetyl group of GlcNAc indicate? a. carbohydrate availability b. fatty acid availability c. protein availability d. diabetes e. oligosaccharide structure

Answer 28

b. fatty acid availability

Question 29

What is the minimal number of negatively charged carboxylate or sulfate groups in one unit of glycosaminoglycan? a. 1 b. 2 c. 3 d. 4 e. 5

Answer 29

a. 1

Question 30

What is the cause of mucopolysaccharidosis? a. inability to degrade amino sugars b. overproduction of carbohydrates c. inability to degrade glycosaminoglycans d. dysregulation of GlcNAc transferase e. inability to synthesize amino sugars

Answer 30

c. inability to degrade glycosaminoglycans

Question 31

Hyaluronate in the cartilage acts as a: a. repeating unit of the aggrecan molecule. b. central filament for the aggrecan molecule. c. monomer of chondroitin sulfate. d. central filament of the aggrecan molecule. e. central filament between glycosaminoglycans.

Answer 31

b. central filament for the aggrecan molecule.

Question 32

What property is the basis for the proteoglycans of the cartilage to function as a shock absorber? a. Reversible nature of the bonds between negatively charged glycosaminoglycans and water. b. Reversible nature of the glycosidic bonds within proteoglycans. c. Irreversible nature of the glycosidic bonds within proteoglycans. d. Irreversible nature of the bonds between glycosaminoglycans and water. e. Reversible nature of the bonds between negatively charged carboxylate or sulfate groups and the proteins.

Answer 32

a. Reversible nature of the bonds between negatively charged glycosaminoglycans and water.

Question 33

Which class of glycoproteins is characterized by the extensive O-glycosylation by N-acetylgalactosamine? a. chitins b. proteoglycans c. mucins d. simple glycoproteins e. glycosaminoglycans

Answer 33

c. mucins

Question 34

. Which carbohydrate defines the B blood type? a. galactose linked to another galactose by an α-1,2 glycosidic bond b. N-acetylgalactosamine linked to galactose by an α-1,2 glycosidic bond c. galactose linked to N-acetylglucosamine by an α-1,3 glycosidic bond d. galactose linked to another galactose by an α-1,3 glycosidic bond e. N-acetylgalactosamine linked to galactose by an α-1,3 glycosidic bond

Answer 34

d. galactose linked to another galactose by an α-1,3 glycosidic bond

Question 35

What is the main function of lectins? a. inflammatory response b. glycosylation c. protein transport from the Golgi complex d. lubricants e. cellular contacts

Answer 35

c. protein transport from the Golgi complex

Question 36

What lectin selectively binds to the endothelium? a. L-selectin b. E-selectin c. P-selectin d. hemagglutinin e. erythropoietin

Answer 36

b. E-selectin

Question 37

Which statement regarding isomeric forms of carbohydrates is TRUE? a. Enantiomers of glyceraldehyde differ in the configuration of two asymmetric centers. b. Epimers appear due to a new asymmetric carbon that forms upon cyclization of a carbohydrate. c. Existence of the stereoisomers doesn't prevent existence of constitutional isomers for a particular carbohydrate. d. Diastereoisomers differ in the same asymmetric carbon. e. Among glucose anomers, the α form is the most abundant.

Answer 37

c. Existence of the stereoisomers doesn't prevent existence of constitutional isomers for a particular carbohydrate.

Question 38

What is an example of a glycosaminoglycan? a. UDP b. glycogen c. cellulose d. lectins e. heparin

Answer 38

c. cellulose

Question 39

Select all that apply. Carbohydrates are _____ with two or more hydroxyl groups. a. aldehydes b. ketones c. acids d. alcohols e. phenols

Answer 39

a. aldehydes b. ketones

Question 40

Which amino acid residues in glycoproteins are the sugars commonly linked to? a. tyrosine and asparagine b. serine, threonine, and asparagine c. serine, tyrosine, and asparagine d. serine and threonine e. tyrosine, serine, threonine, and asparagine

Answer 40

b. serine, threonine, and asparagine

Question 42

Inhibitors against which viral enzyme have potential as anti-influenza agents? Select all that apply. a. calnexin b. neuraminidase c. selectin d. glycosyltransferase e. sialidase

Answer 42

b. neuraminidase/ c. selectin

Question 43

All of the following are repeating units of glycosaminoglycans EXCEPT: a. chondroitin 6-sulfate. b. keratin sulfate. c. hyaluronate. d. heparin. e. hemoglobin.

Answer 43

c. hyaluronate.

Question 44

Which enzyme digests amylopectin? a. α-amylase b. amylose c. cellulose d. lactase e. invertase

Answer 44

a. α-amylase

Question 45

An aldehyde and alcohol can react to form a(n): a. hemialkyl. b. hemiketal. c. hemiacetal. d. amidyl. e. carbonyl.

Answer 45

c. hemiacetal.

Question 46

Select all that apply. The simplest carbohydrates are: a. D-glyceraldehyde. b. glycerate. c. dihydroxyacetone. d. L-glyceraldehyde. e. D-mannose.

Answer 46

a. D-glyceraldehyde./ c. dihydroxyacetone./ e. D-mannose.

Question 47

Select all that apply. Glycoproteins are normally: a. found on membranes. b. secreted as extracellular proteins. c. found inside organelles. d. found inside the nucleus. e. composed of structural components.

Answer 47

a. found on membranes./ b. secreted as extracellular proteins./ c. found inside organelles.

Question 48

Select all that apply. The nutritional storage forms of glucose in plants are: a. glycogen. b. amylose. c. amylopectin. d. starch. e. hemoglobin.

Answer 48

b. amylose. c. amylopectin. d. starch.

Question 49

. Some viruses gain entry into specific cells by: a. attaching to ion channels. b. cleaving the glycosidic bonds and altering protein shapes. c. binding to glycoproteins on the cell surface that are unique to specific cells. d. adding moieties of sialic acids to membrane proteins. e. changing permeability of membranes.

Answer 49

c. binding to glycoproteins on the cell surface that are unique to specific cells.

Question 50

What type of the glycosidic bond is there in this disaccharide? a. β-1,5 linkage b. α-1,4 linkage c. β-1,3 linkage d. α-1,3 linkage e. β-1,4 linkage

Answer 50

e. β-1,4 linkage

Question 51

Select all that apply. Lectins are proteins that: a. bind carbohydrates on glycoproteins and other macromolecules. b. promote cell-cell interaction. c. are found in animals and plants. d. exploit noncovalent interactions for binding carbohydrates. e. are never found in bacteria.

Answer 51

a. bind carbohydrates on glycoproteins and other macromolecules. b. promote cell-cell interaction. c. are found in animals and plants. d. exploit noncovalent interactions for binding carbohydrates.