Mode of action of enzymes — common mistakes

When asked to describe enzyme action, always mention the active site, substrate, enzyme-substrate complex, and the crucial role of lowering activation energy. Differentiating between the lock-and-key and induced-fit models shows a deeper understanding, with induced-fit being the more accurate and comprehensive explanation in most contexts.

Enzymes lower activation energy by forming an enzyme-substrate complex at their active site. This complex can strain substrate bonds, bring reactants into optimal proximity and orientation, or create a favourable microenvironment, effectively providing an alternative reaction pathway that requires less energy to initiate. For more details, explore our free premium lessons and past papers on this topic!

The lock-and-key model proposes a rigid, pre-formed active site perfectly complementary to the substrate. The induced-fit model, however, suggests the active site is flexible, undergoing slight conformational changes upon substrate binding to create an optimal fit. The induced-fit model is generally preferred as it better explains the dynamic nature of enzyme action and transition states. Check out our comprehensive resources for Cambridge 9700 Biology to deepen your understanding.

Enzyme specificity ensures that only specific reactions occur at the right time and place, preventing unwanted side reactions. This precise control is crucial for maintaining metabolic pathways, regulating cellular processes, and ensuring overall biological efficiency and survival. Master enzyme specificity with our premium revision materials and practice questions for the 9700 syllabus.