Biology (0610) Enzymes Revision Note

This document provides a detailed explanation of enzymes for CAIE IGCSE Biology. Enzymes are defined as biological catalysts—special proteins that speed up metabolic reactions without being consumed. They lower activation energy and are essential for sustaining life, functioning repeatedly through the lock and key model, where a substrate fits into the enzyme’s active site to form a product. The guide explores how temperature and pH affect enzyme activity. At the optimum temperature (≈37°C in humans), reactions occur most efficiently. Higher temperatures cause denaturation, altering the active site so substrates can no longer bind, while lower temperatures slow molecular movement, reducing enzyme-substrate complex formation. Similarly, enzymes have an optimum pH, and deviations can break hydrogen bonds, denaturing the enzyme. Examples include pepsin (acidic), amylase (neutral), and trypsin (alkaline). The resource also emphasizes enzyme specificity, protein structure variations, and the importance of conditions for effective activity. Graphs on enzyme activity trends with temperature and pH changes are included for clarity. With its clear explanations, this guide helps students understand enzyme properties, the lock and key hypothesis, and factors influencing enzyme function, preparing them for exam questions.