Assessment

Which of the given sugars does not belong to the group?

• 
• 
• 
• 

Answer explanation

All of the sugars are aldoses as they have aldehydes. Only the L-erythrulose has a carbonyl (C=O) group. It is a ketotetrose.

Classify the given sugar.

• Homopolysaccharide, unbranched

• Heteropolysaccharide, unbranched

• Homopolysaccharide, branched

• Heteropolysaccharide, branched

The process of converting polysaccharides into simple monosaccharides is via (a)   .

*the number of blanks does not necessarily correspond to the number of letter.

Answer explanation

Starch (polysaccharides) from vegetables can be converted to glucose via continuous hydrolysis. Hydrolysis is the breakdown of large molecules into smaller molecules using hydrolase enzymes like amylase. Amylase adds water to break the amylose into shorter molecules.

Based on the photo, the molecule on the right is an stereoisomer of (a)   ?

*the number of blank does not necessarily correspond to the number of letter

Answer explanation

GLUCOSE and GALACTOSE are stereoisomers of each other. They only differ in the 4th carbon where OH is on the left for galactose. FRUCTOSE is a structural isomer of glucose and galactose.

Based on the given image, the molecules are __________?

• Epimers

• Diastereomers

• Enantiomers

• Rotamers

Answer explanation

Enantiomers and Diastereomers are stereoisomers. It means both are isomers that differ in the arrangement of OH and H. It is enantiomer if the difference in arrangement are mirror-like, while it is diastereomer if it is not mirror-like.

D-glucose and D-altrose are examples of ?

• Epimers

• Rotamers

• Diastereomers

• Enantiomers

Based on the given chart, which of the following statements is not correct?

• Galactose and glucose are stereoisomers, but not enantiomers.

• Glucose and fructose are stereoisomers, but not enantiomers.

• Glucose and altrose are stereoisomers and diastereomers.

• All are correct.

Answer explanation

Glucose, Altrose, Mannose and Galactose are stereoisomers as they have the same chemical formula, but differ in arrangement of OH and H in space. They are diastereomers as they do not mirror each other.

Which of the following is an epimer of glucose at C2?

• 
• 
• 
• 

Answer explanation

D and L-glucose are enantiomers. L-glucose and L-galactose are epimers at C4. D-glucose and D-mannose are epimers at C2.

Based on the Fischer projection, what will be the B-configuration of this sugar when converted to Haworth structure?

• 
• 
• 
• 

Answer explanation

REMEMBER:

Right - Down

Left - UP

a-configuration: opposite

b-configuration: same

Which 2 molecules are anomers of each other?

• 
• 
• 
• 

Answer explanation

Anomers are epimers at the anomeric carbon. When the sugar is in its cyclic form, the carbon bonded to the ring oxygen and a hydroxyl group in the cyclic form is the anomeric carbon.