Question

An example of a monosaccharide is ________.

a. fructose

b. glucose

c. galactose

d. all of the above

Short answer

Fructose, glucose, and galactose are all examples of monosaccharides. Hence, an example of a monosaccharide is all of the above.

Step-by-step solution

Introduction

Monosaccharides are sugars consisting of three to seven carbon atoms that cannot be hydrolyzed further to a simpler form. They serve as energy sources for the cell and building blocks for complex carbohydrates. They are classified by the number of carbon atoms they contain such as triose, tetrose, pentose, hexose, and heptose. Hexoses are the most abundant monosaccharides. Monosaccharides are also classified based on the position of the carbonyl group. If the carbonyl group is located at the end of the chain, it is called an aldose. If the carbonyl group is located in the middle of the chain it is called a ketose.

Explanation

Fructose is a six-carbon ketose and hence classifies as a monosaccharide. It is also known as fruit sugar and provides energy to the cells. It combines with glucose to form sucrose, a disaccharide. Hence, option a is correct.

Glucose is a six-carbon aldose and hence is a monosaccharide. It is the major source of energy for the cell. It is also the building block for complex carbohydrates like cellulose and starch. Hence, option b is correct.

Galactose is a six-carbon aldose and hence a monosaccharide. It combines with glucose to form lactose, a disaccharide. Newborn mammals have enzymes that breakdown lactose in milk to galactose which is used as a source of energy. Hence, option c is correct.

Fructose, glucose, and galactose are all monosaccharides. Hence, option d is correct.