What happens to an enzyme's active site when it is denatured?

When an enzyme is denatured, the structure of its active site changes shape. This alteration in shape occurs due to factors such as extreme temperatures or pH levels that disrupt the bonds maintaining the enzyme's three-dimensional structure. The active site is specifically designed to bind to its substrate, allowing the enzyme to catalyze reactions. If the active site changes shape, it can no longer fit the substrate effectively, resulting in a loss of enzymatic activity. This is why the correct answer focuses on the change in shape of the active site, which directly impacts the enzyme's function.