A Level Biology Practice Exam

What type of sugar is a pentose monosaccharide?

1. A sugar with three carbons

2. A sugar with four carbons

3. A sugar with five carbons

4. A sugar with six carbons

The correct answer is: A sugar with five carbons

A pentose monosaccharide specifically refers to a sugar molecule that contains five carbon atoms. The term “pentose” itself is derived from the Greek word for five, emphasizing that the structure of this type of sugar consists of five carbon atoms in the backbone. Common examples of pentose sugars include ribose and deoxyribose, which play crucial roles in nucleotides and nucleic acids, such as RNA and DNA. In contrast, sugars with three, four, or six carbon atoms do not fit this definition. A sugar with three carbons would be classified as a triose, four carbons would indicate a tetrose, and a sugar with six carbons is known as a hexose. Each of these types has distinct biochemical properties and functions that differentiate them from pentoses.