Final answer:
Non-competitive inhibitors bind to an enzyme at an allosteric site, not the active site, causing a conformational change that prevents substrate binding and decreases enzyme activity. This effect is not reversible by adding more substrate since the inhibition occurs at a different site.
Step-by-step explanation:
Non-competitive inhibitors are molecules that bind to an enzyme at a location other than the active site, known as an allosteric site. Such binding induces a conformational change in the enzyme, altering the shape of the active site and thus preventing the substrate from binding effectively. This process, called allosteric inhibition, hinders product formation without directly competing with the substrate for the active site.
The result is a decrease in enzyme activity since the enzyme-substrate complex forms less efficiently or does not produce products at the normal rate. Unlike competitive inhibition, where adding more substrate can overcome the effect of the inhibitor, non-competitive inhibition is not reversible by increasing substrate concentration because the inhibitor's binding site is distinct from the active site.