A Level Biology Practice Exam

What defines a hexose monosaccharide?

1. A monosaccharide composed of six carbons

2. A type of disaccharide

3. A carbohydrate made of five carbons

4. A sugar that contains no water

The correct answer is: A monosaccharide composed of six carbons

A hexose monosaccharide is defined as a monosaccharide that is composed of six carbon atoms. This classification is based on the structure of the molecule, where a hexose has the general formula \(C_6H_{12}O_6\), reflecting its six carbon atoms along with the associated hydrogen and oxygen atoms consistent with carbohydrate chemistry. The other options are less accurate in relation to the definition of a hexose. For instance, a disaccharide consists of two monosaccharide units, so it cannot be defined as a hexose monosaccharide. A carbohydrate made of five carbons is referred to as a pentose, not a hexose. Lastly, the idea that a sugar contains no water is misleading; all carbohydrates, including hexoses, are often illustrated with a formula indicating water molecules as part of their constituent elements. Therefore, the correct characterization of a hexose monosaccharide is solely its six carbon structure.