(a) What are inhibitors? (b) What possible mechanisms account for their effectiveness?

Inhibitors are substances that can decrease or slow down the rate of a chemical reaction, typically by interacting with one or more of the reactants. In the context of enzymatic reactions, inhibitors are molecules that bind to enzymes and reduce their activity, potentially regulating the rate of biochemical reactions.

There are several mechanisms by which inhibitors can exert their effects. We will discuss three main types of inhibition: competitive, non-competitive, and uncompetitive. 1. Competitive Inhibition: In this type of inhibition, the inhibitor competes with the substrate for binding to the active site of the enzyme. The reaction rate decreases because the inhibitor blocks the substrate from binding. It can be overcome by increasing the concentration of the substrate. 2. Non-competitive Inhibition: In non-competitive inhibition, the inhibitor binds to a site other than the active site (called the allosteric site) on the enzyme. This binding causes a conformational change in the enzyme, which in turn alters the active site's shape, making it less effective or less able to bind to the substrate. This type of inhibition cannot be overcome by increasing the substrate's concentration. 3. Uncompetitive Inhibition: Uncompetitive inhibition occurs when the inhibitor binds only to the enzyme-substrate complex, not to the free enzyme. This decreases the concentration of the enzyme-substrate complex, ultimately slowing down the reaction rate. Since the inhibitor does not bind to the free enzyme, increasing the substrate concentration cannot overcome this type of inhibition. In summary, inhibitors are substances that slow down chemical reactions by interacting with the reactants, particularly enzymes. Their effectiveness mainly relies on various mechanisms, including competitive, non-competitive, and uncompetitive inhibition, depending on their binding and interaction with enzymes.