Question

Which of the following is a pentose sugar?

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

Answer 1

The correct option is A

Ribose

Explanation for correct option:

A. Ribose

Carbohydrates:

• "The carbohydrates may be defined as optically active polyhydroxy aldehydes or ketones or the compounds which produce such units on hydrolysis."
• “Some of the carbohydrates, which are sweet in taste, are also called sugars.”
• The most common sugar is sucrose.

Ribose:

• Ribose is a simple sugar as well as a carbohydrate with a chemical formula ${\mathrm{C}}_5{\mathrm{H}}_{10}{\mathrm{O}}_5$.
• It is classified as pentose sugar as it contains five carbon atoms.
• The structure of ribose is given below:

Explanation for incorrect options:

B. Glucose is an aldohexose(a carbohydrate compound consisting of six carbon atoms and an aldehyde group) sugar with a chemical formula ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$.

C. Fructose is a ketonic simple sugar(ketohexose-that contains a ketone group) with a chemical formula ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$.

D. Cellulose is a polysaccharide with a general chemical formula ${\left({\mathrm{C}}_6{\mathrm{H}}_{10}{\mathrm{O}}_5\right)}_n$.

Hence, the correct option is A i.e. Ribose.