Optometry Admission Test (OAT) Practice

Which of the following describes reversible inhibition?

1. Inhibition that permanently alters enzyme structure

2. Competitive inhibitors binding to the active site

3. Active site block by irreversible agents

4. Allosteric inhibitors enhancing enzyme functions

The correct answer is: Competitive inhibitors binding to the active site

Reversible inhibition refers to a type of enzyme inhibition where the inhibitor can bind to and dissociate from the enzyme, allowing for the possibility of the enzyme returning to its active form. In the context of competitive inhibitors, these substances specifically compete with the substrate for binding at the active site of the enzyme. This competition can be overcome by increasing substrate concentration, thereby allowing the enzyme to function again. Focusing on the other choices, the first choice discusses permanent alterations to enzyme structure, which characterizes irreversible inhibition, rather than reversible inhibition. The third option also points to irreversible agents, which lead to a permanent blockade of the active site. Lastly, the fourth choice describes allosteric inhibitors that enhance enzyme functions, which typically involve binding to sites other than the active site and may not fit the definition of inhibition at all. Therefore, competitive inhibitors binding to the active site is the correct description of reversible inhibition.