A Level Biology Practice Exam

What effect does an enzyme inhibitor have on a metabolic pathway?

1. It accelerates the reactions

2. It intensifies substrate binding

3. It slows down the metabolic reactions

4. It stops all enzyme activity

The correct answer is: It slows down the metabolic reactions

Enzyme inhibitors play a crucial role in regulating metabolic pathways by reducing the activity of enzymes. When an enzyme inhibitor is present, it binds to the enzyme, which can lead to a decrease in the enzyme's ability to catalyze reactions effectively. This mechanism slows down the entire metabolic pathway since the reaction rate is dependent on the availability and activity of the enzymes involved. Inhibitors can act in different ways, such as competitive inhibitors, which compete with the substrate for the active site of the enzyme, or non-competitive inhibitors, which bind to a different site and alter the enzyme's function. Regardless of the type, the net effect is a reduction in the overall rate of the metabolic reactions within the pathway. The options that suggest an increase in reaction speed or enhanced substrate interaction misrepresent the role of inhibitors, as their primary function is to decrease enzyme activity and thereby slow down metabolic processes. While some inhibitors may halt specific activities of certain enzymes, they do not completely stop all enzyme activity within a cell, as many pathways and enzymes may still function uninterrupted.