Enzymes, substrates, and active sites
Enzymes, substrates, and active sites

Enzymes are biological catalysts made by living cells. They speed up chemical reactions without being used up, so one enzyme can be reused many times.
Step-by-step lessons covering Edexcel GCSE Biology 1.3 Enzymes for Foundation and Higher tier. Each lesson breaks down 1.3.1 Mechanism of enzyme action, 1.3.2 Denaturation of enzymes, 1.3.3 Factors affecting enzyme activity, and 1.3.4 Measuring energy in food by calorimetry, then works through exam-style questions in Paper 1 and Paper 2 format. Start with the foundational topics and build up to the higher-tier material.