20. Carbohydrates

Draw the structures of a ketohexose.

How many chiral carbon atoms are present in each of the molecules shown in Problem 20.31?

a.

b.

c.

d.

Draw the open-chain structure of a 4-carbon deoxy sugar.

Draw the structures of an aldopentose.

Draw the Fischer projection for each of the following wedge–dash structures:

a.

Draw the Fischer projection for each of the following wedge–dash structures:

a.

An infant with galactosemia can utilize D-glucose in milk but not d-galactose. How does the Fischer projection of D-galactose differ from that of D-glucose?

D-Fructose is the sweetest monosaccharide. How does the Fischer projection of D-fructose differ from that of D-glucose?

What are the differences in the Fischer projections of d-fructose and d-galactose?

On an exam, a student was asked to draw the Fischer projection of L-glucose, but he had only memorized the structure of D-glucose. He wrote the structure of D-glucose and switched the hydroxyl group on C5 from the right to the left. Was his answer correct? If not, what is the name of the aldose that he drew?