A Level Biology Practice Exam

What part of the enzyme does a non-competitive inhibitor bind to?

1. The active site

2. The substrate

3. An allosteric site

4. The regulatory site

The correct answer is: An allosteric site

A non-competitive inhibitor binds to an allosteric site on the enzyme, which is a location distinct from the active site where the substrate binds. By binding to the allosteric site, the non-competitive inhibitor induces a conformational change in the enzyme structure, impacting its functionality. This change prevents the substrate from effectively catalyzing the reaction, regardless of whether the substrate is already bound to the active site or not. This mechanism of inhibition is significant because it allows the non-competitive inhibitor to reduce the overall activity of the enzyme without directly blocking the active site where the substrate would otherwise attach. This type of inhibition can be observed with various enzymes in metabolic pathways and can influence how enzymes respond to substrates under different cellular conditions.