A Level Biology Practice Exam

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What type of molecule is starch?

Amino acid
A polysaccharide
A monosaccharide
A disaccharide

The correct answer is: A polysaccharide

Starch is a type of polysaccharide, which is a large macromolecule made up of long chains of glucose units linked together. It serves as a significant energy storage molecule in plants. Starch consists of two components: amylose, which is linear, and amylopectin, which is branched. Being a polysaccharide means that it is composed of many sugar (glucose) molecules joined together, allowing it to store energy efficiently. In contrast, other options represent different classes of carbohydrates. Amino acids are the building blocks of proteins, while monosaccharides are simple sugars like glucose, and disaccharides are formed from two monosaccharide molecules, such as sucrose. Understanding these definitions helps clarify why starch is correctly identified as a polysaccharide.