Question

Which of the following pairs is a monosaccharide?
A. Glucose and Fructose
B. Glucose and Sucrose
C. Ribose and Maltose
D. Ribose and Sucrose

Answer 1

Monosaccharides are also called simple sugar that serve as the building blocks of other complex carbohydrates. All monosaccharides have the formula ${\left( {C{H_2}O} \right)_n}$. They can be joined together by glycosidic linkages to generate oligosaccharides or polysaccharides, which are bigger carbohydrates. Monosaccharides are Polyhydroxy aldehydes or ketones based on the position of carbonyl group.

Complete answer:
Option A Glucose and Fructose: Glucose and Fructose are monosaccharides with the formula${C_6}{H_{12}}{O_6}$. They are the most basic carbohydrates. The difference between glucose and fructose is based on the position of the carbonyl group. Glucose is a simple aldose sugar while fructose is a simple ketogenic sugar.
Option A is correct.
Option B Glucose and Sucrose: While Glucose is a monosaccharide, Sucrose is a disaccharide made up of two monosaccharide molecules- glucose and fructose. Sucrose has a molecular formula${C_{12}}{H_{22}}{O_{11}}$. Sucrose is also called cane sugar.
Option B is incorrect.
Option C Ribose and Maltose: Ribose is a monosaccharide with molecular formula ${C_5}{H_{10}}{O_5}$. Their naturally occurring form D-ribose is a component of the ribonucleotides from which RNA is built. This molecule is required for gene coding, decoding, and expression. Maltose is a disaccharide made up of two glucose molecules. Their molecular formula is ${C_{12}}{H_{22}}{O_{11}}$.
Option C is incorrect.
Option D Ribose and Sucrose: Ribose is a monosaccharide whereas sucrose is a disaccharide hence this option cannot be correct.
Option D is incorrect.

Hence, Option A. Glucose and Fructose is the right answer.

Note:
In the structure of monosaccharide, the two hydrogen atoms and one oxygen atom are bonded to the central carbon molecule. One of the major functions of monosaccharide is to act as an energy source for living organisms. They are also the foundation for other complex carbohydrates and they serve as components to amino acids.