Question

Which of these is not an aldose sugar?

• A. Glucose
• B. Mannose
• C. Fructose
• D. Ribose

Answer 1

The correct option is C Fructose

Aldose and ketose are two different types of sugars, which are named on the basis of presence of functional group, aldehyde or ketone. The sugars which contain aldehyde(-CHO) as a functional group are named as aldoses, while sugars which contain Ketone(-CO-) as a functional group are called as ketoses. In the given question glucose, ribose, and mannose, contains aldehyde as a function group and therefore are examples of aldoses. However, fructose contains a Ketone group and therefore it is a ketose and not aldose.

So, the correct answer is 'Fructose'.