Enzyme Structure and Function

Enzymes are biological catalysts made of globular proteins that play a crucial role in facilitating biochemical reactions. They maintain their highly specific shape through chemical bonds such as hydrogen bonds, ionic bonds, and disulphide bridges.

Definition: Enzymes are biological catalysts that speed up chemical reactions without being permanently changed in the process.

The active site of an enzyme is formed by a small number of amino acids in the polypeptide chains, but the overall shape is determined by the entire amino acid sequence and the bonds formed during protein folding.

Highlight: Enzymes can be found both intracellularly and extracellularly, participating in anabolic (building) and catabolic (breaking) reactions.

Collision Theory and Enzyme Action

Collision theory explains how enzymes work at the molecular level:

1. Molecules move randomly due to kinetic energy.
2. Reactions occur when molecules collide with sufficient energy to overcome the activation energy barrier.
3. Enzymes lower this activation energy, making reactions more likely to occur.

Example: In the induced fit model of enzyme action, the enzyme's shape changes slightly to accommodate the substrate, forming an enzyme-substrate complex. This model is crucial for understanding enzyme active site interaction in AQA Biology GCSE and A-level.

Enzyme Action Diagram

The document includes a diagram illustrating enzyme action, comparing the energy profiles of reactions with and without enzymes. It shows how enzymes lower the activation energy required for a reaction to occur.

Vocabulary: Activation energy is the minimum energy required for a chemical reaction to take place.