OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What are proteins made of?

1. Chains of fatty acids

2. Chains of nucleotides

3. Chains of amino acids

4. Chains of sugars

The correct answer is: Chains of amino acids

Proteins are composed of chains of amino acids, which are organic compounds containing both an amino group and a carboxyl group. Amino acids link together through peptide bonds to form polypeptides, which then fold into specific three-dimensional structures to create functional proteins. The unique sequence of amino acids determines the protein’s structure and function, making them essential for a wide range of biological processes in living organisms, including enzyme activity, cell signaling, and structural support. The other options refer to different types of biological macromolecules: fatty acids are the building blocks of lipids, nucleotides are the units that make up nucleic acids like DNA and RNA, and sugars are the basic components of carbohydrates. Each class of biomolecule plays distinct roles in biological systems, with proteins being particularly vital due to their diverse functions.