Question

How many isomers does D-mannose have?

a) 2 isomers: D-mannose and L-mannose
b) 3 isomers: α-D-mannose, β-D-mannose, and L-mannose
c) 4 isomers: α-D-mannose, β-D-mannose, L-mannose, and D-mannose-6-phosphate
d) 5 isomers: α-D-mannose, β-D-mannose, L-mannose, D-mannose-6-phosphate, and D-mannose-1-phosphate

Answer 1

The correct answer is c) 4 isomers: α-D-mannose, β-D-mannose, L-mannose, and D-mannose-6-phosphate

Step-by-step explanation:

The correct answer is c) 4 isomers: α-D-mannose, β-D-mannose, L-mannose, and D-mannose-6-phosphate. D-mannose is a diastereomer of D-glucose, and it differs from D-glucose in the configuration of only one chiral center. There are two sets of epimers of D-mannose based on the configurational change at C#2: α-D-mannose and β-D-mannose. In addition, D-mannose can also exist in phosphorylated form as D-mannose-6-phosphate.