Assessment and Qualifications Alliance (AQA) GCSE Chemistry Paper 2 Practice Exam 2025 - Free GCSE Chemistry Practice Questions and Study Guide

When different amino acids combine to form polypeptides, the end product is proteins. Polypeptides are long chains made up of amino acids linked together through peptide bonds. When these polypeptides fold into specific three-dimensional structures, they become functional proteins. Proteins play crucial roles in various biological processes, including acting as enzymes, structural components, and transport molecules.

The other options represent different types of biomolecules. Enzymes are a subset of proteins that function as catalysts in biochemical reactions, but they are not the direct product of the combination of amino acids themselves. Polysaccharides are carbohydrates formed from sugar molecules, and lipids are a diverse group of hydrophobic molecules, which include fats and oils. None of these options involve the direct combination of amino acids into polypeptide chains, which is specifically what results in protein formation.