Deck 23: Carbohydrates and Nucleic Acids

Question 1

L-Ribulose may be classified as ________.

A) an aldotetrose
B) an aldopentose
C) an aldohexose
D) a ketotetrose
E) a ketopentose

Answer 1

a ketopentose

Question 2

List the aldohexoses described by the mnemonic "All altruists gladly make gum in gallon tanks."

Answer 2

allose, altrose, glucose, mannose, gulose, idose, galactose, and talose

Question 3

Most monosaccharides are highly water soluble. Offer an explanation.

Answer 3

The presence of a large number of hydroxyl groups on a relatively small organic molecule results in high water solubility. Favorable hydrogen bonding between monosaccharides and water occurs readily.

Question 4

Draw the Fischer projection for the open-chain form of D-erythrose.

Question 5

Draw the Fischer projection of the open chain form of D-arabinose.

Question 6

Draw the structure of D-glyceraldehyde.

Question 7

A γ-Hydroxyaldehyde may cyclize to form:

A) a hemiacetal.
B) an ester.
C) a pyrimidine.
D) a lactone.
E) a lactam.

Question 8

List the aldopentoses described by the mnemonic "Ribs are extra lean."

Question 9

Draw the Fischer projection for the open-chain form of D-glucose.

Question 10

_{How many molecules of carbon dioxide and water are needed to make a molecule of glucose in photosynthesis?}

A) 5 CO₂ and 5 H₂O
B) 5 CO₂ and 6 H₂O
C) 6 CO₂ and 6 H₂O
D) 6 CO₂ and 2 H₂O
E) 2 CO₂ and 2 H₂O

Question 11

Draw the Fischer projection of the open chain form of L-allose.

Question 12

All chiral D-sugars rotate plane-polarized light:

A) clockwise.
B) counterclockwise.
C) +20.0°.
D) in a direction that cannot be predicted but must be determined experimentally.
E) since they are optically inactive.

Question 13

Draw the Fischer projection for the open-chain form of D-fructose.

Question 14

Provide the structure of the open-chain form of D-galactose.

Question 15

All naturally occurring sugars can be degraded to:

A) D-(-)-glyceraldehyde.
B) D-(+)-glyceraldehyde.
C) L-(-)-glyceraldehyde.
D) L-(+)-glyceraldehyde.
E) none of the above

Question 16

The structure of D-arabinose is shown below. Which of the following correctly describes the configurations of the asymmetric carbons in D-arabinose?

A) 2S, 3R, 4R
B) 2R, 3S, 4S
C) 2S, 3R, 4S
D) 2R, 3S, 4R
E) 2S, 3S, 4R

Question 17

Provide the structure of the open-chain form of L-altrose.

Question 18

How many asymmetric centers are present in the open chain form of the aldohexose D-(-)-gulose?

A) 0
B) 1
C) 2
D) 4
E) 5

Question 19

In the Fischer projection of D-(+)-glyceraldehyde, the hydroxyl group on the asymmetric carbon center is:

A) on the bottom.
B) on the top.
C) at the left.
D) at the right.
E) present as a hemiacetal.

Question 20

Given the structure of D-altrose below, draw the structure of L-altrose.

Question 21

In solution, glucose exists as:

A) the open-chain form only.
B) the cyclic hemiacetal form only.
C) an equilibrium mixture of the open-chain form and cyclic acetal forms.
D) an equilibrium mixture of the open-chain form and cyclic hemiacetal forms.

Question 22

Fructose forms:

A) a five-membered cyclic hemiacetal.
B) a six-membered cyclic hemiacetal.
C) a six-membered lactone.
D) a five-membered lactone.
E) none of the above

Question 23

Draw the Haworth structure of a-D-glucopyranose.

Question 24

Which of the following descriptions apply to both dihydroxyacetone and D-fructofuranose?
I. They are both ketoses.
II. They are both aldoses.
III. They are enatiomers of each other.
IV. They are diastereomers of each other.
V. They are epimers of each other.

A) I
B) II
C) I and III
D) II and IV
E) II, IV and V

Question 25

Which of the following descriptions apply to both D-glucopyranose and L-galactopyranose?
I. They are both ketoses
II. They are both aldoses
III. They are enantiomers of each other
IV. They are diastereomers of each other
V. They are epimers of each other

A) I, III and V
B) II and III
C) I, IV and V
D) II and IV
E) II, IV and V

Question 26

Draw the more stable chair conformer of α-D-glucopyranose.

Question 27

How many asymmetric carbons are present in a-D-ribopyranose?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 28

Which of the following represents a pair of epimers?

A) D- and L-erythrose
B) D-erythrose and D-threose
C) D-arabinose and D-erythrose
D) D-arabinose and D-xylose
E) D-glyceraldehyde and D-threose

Question 29

Draw the Haworth structure of b-D-ribofuranose.

Question 30

A diastereomer is called erythro if its Fischer projection shows similar groups:

A) opposite each other on the same carbon.
B) equally spaced about a central carbonyl.
C) directly above and below a central carbonyl.
D) on the same side of the molecule on adjacent carbons.
E) on opposite sides of the molecule on adjacent carbons.

Question 31

Identify the C₃ epimer of the sugar below drawn in its open chain (acyclic) Fischer projection.

A)

B)

C)

D)

Question 32

Draw the Haworth structure of β-D-glucopyranose.

Question 33

Draw the Haworth structure of α-D-ribofuranose.

Question 34

Draw the Fischer projection of (2S,3R)-2,3-dihydroxybutanoic acid, and label it as erythro or threo.

Question 35

Stereoisomeric aldohexoses that differ in configuration at only a single carbon are:

A) meso compounds.
B) threo sugars.
C) enantiomers.
D) constitutional isomers.
E) epimers.

Question 36

Which of the following correctly describes the structural relationship between D-ribose and L-lyxose?

A) diastereomers and epimers
B) diastereomers but not epimers
C) enantiomers
D) constitutional isomers
E) not isomers

Question 37

When a monosaccharide reacts to give the pyranose form from its open-chain form, how many distinct pyranose forms are possible?

A) 1
B) 2
C). 2 ⁿ, where n is the number of carbons present
D). 4n + 2, where n is the number of carbons present
E) 4

Question 38

Six-membered cyclic hemiacetals and five-membered cyclic hemiacetals are called, respectively,

A) mannoses and xyloses.
B) maltoses and arabinoses.
C) pyranoses and furanoses.
D) glyoses and fructoses.
E) none of the above

Question 39

Which of the following correctly describes the structural relationship between D-gulose and L-gulose?

A) diastereomers and epimers
B) diastereomers but not epimers
C) enantiomers
D) constitutional isomers
E) not isomers

Question 40

In a Haworth projection of a five-membered cyclic hemiacetal,

A) the C6 carbon is drawn on the right.
B) the C2 carbon is drawn on the left.
C) the ring oxygen is drawn in the front.
D) the ring oxygen is drawn in the back.
E) all hydroxyls are always on the same side of the molecule.

Question 41

What are the two most common unwanted side reactions which can occur when monosaccharides are treated with base?

A) epimerization and enediol rearrangement
B) muta rotation and epimerization
C) enediol rearrangement and glycoside formation
D) Kiliani-Fischer and Ruff degradations
E) Ruff degradation and glycoside formation

Question 42

Draw the Haworth structure of the α-pyranose form of the monosaccharide shown below.

Question 43

Draw the Haworth structure of the β-pyranose form of the monosaccharide shown below.

Question 44

When pure α-D-glucopyranose is dissolved in water, the optical rotation of the resulting solution changes over a period of time. What is the name of this phenomenon and why does it occur?

Question 45

Draw the Haworth structure of the α-furanose form of the monosaccharide shown below.

Question 46

Draw the product of the following reaction in a Fischer projection.

Question 47

Anomers of D-glucopyranose differ in their stereochemistry at:

A) C5
B) C4
C) C3
D) C2
E) C1

Question 48

When L-erythrose is treated with NaBH₄,

A) a 70:30 mixture of enantiomeric alditols results.
B) a 50:50 mixture of enantiomeric alditols results.
C) a meso alditol is produced.
D) the product mixture contains two diastereomeric alditols.
E) an optically active alditol is produced.

Question 49

How might one separate α-D-glucopyranose from a solution also containing β-D-glucopyranose.

Question 50

Draw the Haworth structure of the α-pyranose form of the monosaccharide shown below.

Question 51

A pyranose with the hydroxyl group on the anomeric carbon pointing up in the Haworth structure is designated:

A). a
B). b'.
C) α.
D) β.
E) γ.

Question 52

What reagents are needed to induce the following isomerization?

A) NaOH
B) Br₂ / H₂O
C) HCl (aq)
D) PCC

Question 53

Draw the Haworth structure of the β-furanose form of the monosaccharide shown below.

Question 54

The α and β anomers of a D-glucopyranose are related as:

A) enantiomers.
B) meso compounds.
C) structural isomers.
D) epimers.
E) disaccharides.

Question 55

Draw the Haworth structure of the α-pyranose form of the monosaccharide shown below.

Question 56

Reduction of a 2-ketohexose with NaBH_{4 yields:}

A) a single aldohexose.
B) a mixture of acetals.
C) a mixture of alditols.
D) a mixture of cyclic hemiacetals.
E) a single pyranose.

Question 57

Show the Haworth of α-L-fructofuranose and the Fischer diagram of L-fructose.

Question 58

What is the result of reaction involving D-glyceraldehyde and NaBH₄?

A) propane
B) ethanol and CO₂
C) dihydoxyacetone
D) glyceric acid
E) glycerol

Question 59

Provide the Haworth structure of b-D-ribopyranose.

Question 60

Draw the Haworth structure of the α-furanose form of the monosaccharide shown below.

Question 61

What is the major organic product of the following reaction?

Question 62

What is the major organic product of the following reaction?

Question 63

Draw the Haworth structure of ethyl β-D-galactopyranoside.

Question 64

When D-(+)-xylose is treated with nitric acid, which of the following results?

A) a racemic mixture of aldaric acids
B) an optically active aldaric acid
C) an optically inactive aldaric acid
D) an optically active aldonic acid
E) an optically inactive aldonic acid

Question 65

What is the outcome of the following reaction?

A) No Reaction
B)
C)
D)

Question 66

Under what conditions is the methyl glycoside of galactose prepared?

Question 67

Draw the Haworth structure of methyl α-D-xylofuranoside.

Question 68

Provide the Fischer projection of the open-chain form of the aldonic acid which results when L-glucose is treated with bromine water.

Question 69

Which of the following would give a posi tive Tollen's test?

A) α-D-glucopyranose
B) methyl β-D-glucopyranoside
C) sucrose
D) methyl α-D-ribofuranoside
E) none of the above

Question 70

What is the major organic product of the following reaction?

Question 71

What is the major organic product of the following reaction?

Question 72

An aglycone is a group bound to:

A) the oxygen of C6 in a glycoside.
B) the anomeric carbon in a glycoside.
C) a pyrimidine base.
D) a purine base.
E) a xanthate.

Question 73

When L-(+)-idose is treated with _{bromine water, which of the following results?}

A) a racemic mixture of aldaric acids
B) an optically active aldaric acid
C) an optically inactive aldaric acidS
D) an optically active aldonic acid
E) an optically inactive aldonic acid

Question 74

Provide the structure of the product which results when D-ribose is treated with bromine water.

Question 75

Under what conditions is the methyl glycoside of galactose hydrolyzed?

Question 76

When L-(+)-lyxose is treated with nitric acid, which of the following results?

A) a racemic mixture of aldaric acids
B) an optically active aldaric acid
C) an optically inactive aldaric acid
D) an optically active aldonic acid
E) an optically inactive aldonic acid

Question 77

When D-(+)-allose is treated with bromine water, which of the following results?

A) a racemic mixture of aldaric acids
B) an optically active aldaric acid
C) an optically inactive aldaric acid
D) an optically active aldonic acid
E) San optically inactive aldonic acid

Question 78

Which of the following is a reducing sugar?

A) α-D-fructofuranose
B) the methyl glycoside of cellobiose
C) ethyl β-D-glucopyranoside
D) methyl α-D-fructofuranoside
E) none of the above

Question 79

The open-chain form of D-talose is shown below. Draw the chair form of methyl β-D-talopyranoside.

Question 80

Which of the following statements is true?

A) All monosaccharides in either the ketose of aldose family are reducing sugars.
B) Only aldoses, but not ketoses, are reducing sugars.
C) Only ketoses, but not aldoses, are reducing sugars.
D) All disaccharides, not monosaccharides, are reducing sugars.
E) All glycosides are reducing sugars.