Question : 1.Which of the following statements concerning carbohydrates INCORRECT? A) Carbohydrates serve : 1318477

1.Which of the following statements concerning carbohydrates is INCORRECT?

A) Carbohydrates serve important energy and structural roles for plants and animals.

B) Monosaccharides are the simplest carbohydrates and are known as simple sugars.

C) Monosaccharides join together to form disaccharides and polysaccharides by hydrogen bonding.

D) Humans store excess glucose for short term energy requirements in the polysaccharide glycogen.

E) Carbohydrates that can be oxidized by the Benedict’s reagent are known as reducing sugars.

 

2.Monosaccharides are structurally defined as which of the following?

A) polyhydroxy aldehydes or polyhydroxyketones

B) hemiacetals and acetals

C) polyamides or polyesters

D) enols and enolates

E) carboxylic acids

 

3.Carbohydrates are chiral or “handed” biomolecules.  What does the term chiral describe?

A) a molecule that has a mirror image

B) a molecule that can be superimposed on its mirror image

C) a molecule that exists in two nonsuperimposable mirror image forms

D) a molecule that can be digested by the body

E) a molecule that may be synthesized by the body

 

4.Which enantiomer of glyceraldehyde is represented in the following structure?

A) L-glyceraldehyde

B) ?-glyceraldehyde

C) ?-glyceraldehyde

D) D-glyceraldehyde

E) It is impossible to determine from the structure alone.

 

5.Which of the following statements concerning stereochemistry is INCORRECT?

A) Stereoisomers are molecules with the same molecular formula, same bonding pattern, but different spatial arrangement of atoms.

B) A chiral carbon is a carbon atom that has four different groups bonded to it.

C) A molecule that contains a chiral carbon is a chiral molecule, and exists as a pair of enantiomers.

D) Enantiomers are superimposable mirror image stereoisomers.

E) A racemic mixture of enantiomers is optically inactive.

 

6.Propranol is a chiral compound that exists as a pair of enantiomers.  One enantiomer is used to treat irregular heartbeats, and the other is used as a contraceptive.  Which labeled carbon atom(s) is/are chiral?

A) C-1

B) C-2

C) C-3

D) C-4

E) C-1 and C-3

 

7.How does the structure of ?-D-glucose differ from that of ?-D-glucose?

A) ?-D-Glucose is an aldose and ?-D-glucose is a ketose.

B) In ?-D-glucose the −OH group on the last chiral carbon is on the left, and in ?-D-glucose the –OH group on the last chiral carbon is on the right.

C) In ?-D-glucose the −OH group on the hemiacetal carbon is below the ring, and in ?-D-glucose the –OH group on the hemiacetal carbon is above the ring.

D) In ?-D-glucose the last –CH2OH group is on the right, and in ?-D-glucose the −CH2OH group is on the left.

E) There is no structural difference between the two.

 

8.Which carbohydrate is present in RNA?

A) ribulose

B) glucose

C) mannose

D) ribose

E) fructose

 

9.The open chain structure of D-fructose is shown. What is the Haworth projection for ?-D-fructose?

 

A)

 

B)

 

C)

 

D)

 

E)

 

 

10.What product is formed when the monosaccharide below is oxidized by a basic solution of Benedict’s reagent?

A)

B)

C)

D)

E)

 

 

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