Enzymes as catalysts
Enzymes are biological catalysts and are globular proteins. They increase the rate of chemical reactions in living systems without being consumed.
The folded globular structure contains a region called the active site, where a reacting molecule can bind. The molecule that binds is the substrate.
When the substrate is held at the active site, an enzyme–substrate complex is formed.
Binding and reaction
A substrate must collide with the active site in a suitable orientation for effective binding and reaction to occur.
- The substrate approaches the active site.
- Binding produces the enzyme–substrate complex.
- The reaction occurs while the substrate is associated with the enzyme.
- The enzyme remains available for further reactions rather than being consumed.
Exam Tip: When describing an enzyme, state that it is a protein that acts as a biological catalyst. If the substrate is shown bound to the enzyme, identify the combined species as the enzyme–substrate complex.