Lock And Key Systems (PY104.16) Practice Test

Substrate inhibition happens when adding more substrate beyond a certain level actually slows the reaction instead of speeding it up. At very high substrate concentrations, extra substrate molecules can bind to a second, inhibitory site on the enzyme or form a nonproductive complex with the active site. This blocks catalysis and reduces the rate, even though more substrate is present. That’s why the correct description says very high substrate concentrations inhibit enzyme activity by causing additional binding that blocks catalysis. This differs from permanent inactivation, which would destroy enzyme function entirely; product inhibition, where the product rather than the substrate inhibits the enzyme; and the idea of the substrate acting as a competitive inhibitor of itself, which doesn’t fit how competitive inhibition works.