C1.1.4—ENZYMES AS GLOBULAR PROTEINS WITH AN ACTIVE SITE FOR CATALYSIS

Enzymes- globular proteins

Enzymes are typically large, globular protein molecules where the tertiary structure has given the molecule a generally rounded shape

Substrate

In a reaction catalysed by an enzyme, the starting substance is called the substrate - substance on which an enzyme acts

Product

Substrate is converted into product after enzyme activity

How enzyme works

By binding to the substrate molecule, a specially formed pocket in an enzyme - the binding point is called an active site

At the active site

An enzyme- substrate complex is formed- The substrate is raised to a high energy transition state - activation energy is added

Then

This complex has the briefer of existences before the substrate molecule is formed into another molecule or broken down into others by the catalytic properties of the active site.

Then the products are released together with the unchanged enzyme. The enzyme is available for reuse

Role of amino acids in active site

Active site residues (amino acids present) play many different roles.