Deck 21: Biomolecules: Carbohydrates

Question 1

Convert the Fischer projections into tetrahedral representations, and assign R or S stereochemistry to each.
Describe the fundamental difference between the following classifications of carbohydrates.
a.
monosaccharide, disaccharide, polysaccharide
b.
simple sugar, complex sugar
c.
ketose, aldose
d.
furanose, pyranose

Answer 1

a.the number of monosaccharides present
b.whether or not the carbohydrate can be converted into smaller sugars by hydrolysis
c.
the type of carbonyl group present
d.
the presence of a five or six-membered cyclic hemiacetal

Question 2

Refer to the equilibrium below to answer the following question(s).
Refer to instructions. Classify ribose by carbonyl type and number of carbons.

Answer 2

Ribose is an aldopentose.

Question 3

Refer to the monosaccharides below to answer the following question(s). Classify each sugar by type; for example, glucose is an aldohexose.a. Sorbose b. Rhamnose c. Erythrulose d. Xylulose
Refer to instructions. Sorbose is ____________________.

Answer 3

a ketohexose

Question 4

Convert the Fischer projections into tetrahedral representations, and assign R or S stereochemistry to each.
Convert and assign:

Question 5

If the following compound undergoes oxidation in the presence of the appropriate enzyme, draw the structure of the likely product.

Question 6

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.





Refer to instructions. _____ a dextrorotary hexose and ______ a levorototary tetrose.

A)a
B)b
C)c
D)d

Question 7

Refer to the monosaccharides below to answer the following question(s).
a. Sorbose b. Rhamnose c. Erythrulose d. Xylulose
Refer to instructions. Draw both chair conformations of the α-anomer of rhamnose in its pyranose form. Circle the more stable conformation.

Question 8

Refer to the monosaccharides below to answer the following question(s). Classify each sugar by type; for example, glucose is an aldohexose.a. Sorbose b. Rhamnose c. Erythrulose d. Xylulose
Refer to instructions. Erythrulose is ____________________.

Question 9

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.





Refer to instructions. _____ oxidizes to an optically inactive aldaric acid.

A)(−)-tagatose
B)(+)-gulose
C)(−)-erythrose
D)(−)-ribulose

Question 10

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.





Complete the equation for the following reaction.

Question 11

Refer to the monosaccharides below to answer the following question(s).
a. Sorbose b. Rhamnose c. Erythrulose d. Xylulose
Convert the following Fisher projections into tetrahedral representations.

Question 12

Refer to the monosaccharides below to answer the following question(s).
a. Sorbose b. Rhamnose c. Erythrulose d. Xylulose
Refer to instructions. Provide the complete name for the α-anomer of rhamnose in its pyranose form.

Question 13

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.





Using the following structure of D-talose as a guide, draw the structure for α-D-talopyranose. Label each ring substituent as axial or equatorial.

Question 14

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.





Draw the structure of the product of the following reaction.

Question 15

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.





Refer to instructions. _____ a ketose and _____ an aldose with two chirality centers

A)a
B)b
C)c
D)d

Question 16

Convert the Fischer projections into tetrahedral representations, and assign R or S stereochemistry to each.
Convert and assign:

Question 17

Refer to the equilibrium below to answer the following question(s).
Refer to instructions. The correct name for the cyclic structure is____.

A) α-L-ribofuranose
B) β-D-ribofuranose
C) α-L-ribopyranose
D) β-D-ribopyranose

Question 18

Refer to the monosaccharides below to answer the following question(s).
a. Sorbose b. Rhamnose c. Erythrulose d. Xylulose
Refer to instructions. Assign R or S configuration to each chirality center in sorbose.

Question 19

Refer to the equilibrium below to answer the following question(s).
Refer to instructions. Which enantiomer of ribose is drawn, D or L, and is it the α or β anomer?

Question 20

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.
​Refer to instructions. _____ oxidizes to an optically inactive aldaric acid.

A)(-)-tagatose ​
B)(+)-gulose
C)(-)-erythrose
D)(-)-ribulose

Question 21

The monosaccharide shown below is

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

Question 22

The specific rotation of the pure α-anomer of a monosaccharide is +169.7 and that of the pure β-anomer is +29.4. A solution of the pure α-anomer produces a specific rotation of +61.4. Based on this data, which of the following is correct?

A) The solution contains more of the α-anomer.
B) The solution is an equimolar mixture of the two anomers.
C) A solution of the pure β-anomer would produce the same specific rotation.
D) The change in specific rotation is due to the irreversible formation of the open-chain monosaccharide.
E) All of these.

Question 23

What is the correct structure for α-D-glucopyranose?

A)

B)

C)

D)

Question 24

Aldohexoses may exist as furanoses or pyranoses. Aldopentoses also may exist as furanoses or pyranoses.
a)Draw Haworth projections for a furanose and a pyranose obtained from D-ribose.
b)Each product can exist in two anomeric forms. What is the structural difference between these forms?

Question 25

Draw structures for the products you would expect to obtain from reaction of β-D-galactopyranose with the listed reagents. Be sure to include all relevant stereochemistry. β-D-galactopyranose
Draw:
NaBH₄ in H₂O

Question 26

Draw structures for the products you would expect to obtain from reaction of β-D-galactopyranose with the listed reagents. Be sure to include all relevant stereochemistry. β-D-galactopyranose
Draw:
Br₂, H₂O

Question 27

Which of the following could not form a pyranose?

A) D-threose
B) D-ribose
C) D-lyxose
D) D-glucose
E) D-galactose

Question 28

Consider the reaction below to answer the following question(s).
Refer to instructions. Compound Z is:

A) the D-anomer.
B) the α-anomer.
C) the β-anomer.
D) the L-anomer.

Question 29

Consider the reaction below to answer the following question(s).
Refer to instructions. Which anomer is the LEAST stable?
Q or Z

Question 30

Consider the reaction below to answer the following question(s).
Refer to instructions. Q and Z are cyclic examples of:

A) acetals
B) hemiacetals
C) alditols
D) hemialditols

Question 31

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.
Draw the Fisher projection of L-mannose.

Question 32

Draw an aldopentose with S,S,R stereochemistries at its carbons 2 through 4.

Question 33

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.
​Refer to instructions. _____ a ketose and _____ an aldose with two chirality centers

A)(-)-tagatose ​
B)(+)-gulose
C)(-)-erythrose
D)(-)-ribulose

Question 34

Refer to D-iodose below to answer the following question(s).
Refer to instructions. The Fischer projection for D-iodose (above) corresponds to which pyranose below?

A)

B)

C)

D)

Question 35

How many D-ketotetroses could exist?

A) none
B) one
C) two
D) four
E) eight

Question 36

Refer to the carbohydrate below to answer the following questions. a)Which carbon in the carbohydrate is the anomeric carbon?
b)What would be observed on the addition of Tollen's reagent to a solution of this sugar?

Question 37

Draw structures for the products you would expect to obtain from reaction of β-D-galactopyranose with the listed reagents. Be sure to include all relevant stereochemistry. β-D-galactopyranose
Draw:
Ch₃I, Ag₂O

Question 38

Refer to the sugars below to answer the following question(s). Choose the sugar that best fits each description. There is only one correct answer for each question, but sugars may be used more than once. Indicate each answer by the corresponding letter.
​Refer to instructions. _____ a dextrorotary hexose and ______ a levorototary tetrose.

A)(-)-tagatose ​
B)(+)-gulose
C)(-)-erythrose
D)(-)-ribulose

Question 39

Refer to the carbohydrate below to answer the following questions. a)Which carbon in the carbohydrate is the anomeric carbon?
b)Does this represent an α or β-anomoer?

Question 40

Consider the reaction below to answer the following question(s).
Refer to instructions. Place a triangle around the anomeric carbon in compound Q.

Question 41

Choose a structure from the list provided below that best fits the description given. There is only one correct answer for each question.
A non-reducing disaccharide

A)
B)
C)
D)
E)
F)

Question 42

Which of the following is a disaccharide?

A) glucose
B) fructose
C) sucrose
D) N-acetylgalactosamine
E) both c and d

Question 43

What is the relationship between D-erythrose and D-threose?

A) they are constitutional isomers
B) they are enantiomers
C) they are diastereomers
D) they are tautomers

Question 44

Choose a structure from the list provided below that best fits the description given. There is only one correct answer for each question.
A reducing monosaccharide

A)
B)
C)
D)
E)
F)

Question 45

Which of the following has a D-configuration?

A) only 1 and 2
B) only 1 and 3
C) only 2 and 3
D) only 1, 2 and 3

Question 46

Choose a structure from the list provided below that best fits the description given. There is only one correct answer for each question.
A 1,4' β-glycoside

A)
B)
C)
D)
E)
F)

Question 47

Treatment with dilute NaOH can convert

A) an aldose into a ketose
B) an aldose into a carboxylic acid
C) an aldose into its acetate ester
D) a glycoside into a monosaccharide plus an alcohol
E) a monosaccharide plus an alcohol into a glycoside

Question 48

Which reagent would be best suited for the transformation shown?

A) alkaline Cu²⁺ in H₂O
B) Ag⁺ in H₂O/NH₃
C) H₂, with Ni catalyst
D) NaNO₃ at 0°C
E) NaBH₄ in H₂O

Question 49

The brick-red color observed when Benedict's test is applied to D-mannose is due to

A) the reduced form of the Cu²⁺ reagent
B) the reduced form of the D-mannose
C) the oxidized form of the Cu²⁺ reagent
D) the oxidized form of the D-mannose
E) products in the mixture other than those listed