A Level Biology Practice Exam

What is a monosaccharide?

1. A complex carbohydrate molecule

2. A type of amino acid

3. A single sugar molecule

4. A polysaccharide made of multiple sugars

The correct answer is: A single sugar molecule

A monosaccharide is defined as a single sugar molecule, which serves as the most basic unit of carbohydrates. These simple sugars consist of carbon, hydrogen, and oxygen, typically with the formula (CH2O)n, where n is usually between three and seven. Common examples of monosaccharides include glucose, fructose, and galactose. Their structure is characterized by having a carbon backbone with hydroxyl groups (-OH) and a ketone or aldehyde functional group, which makes them the primary building blocks for more complex carbohydrates, such as disaccharides and polysaccharides. This fundamental role in carbohydrate chemistry is essential to many biological processes, including energy production, cellular respiration, and the synthesis of larger carbohydrate molecules.