If enzymes are exposed to very high temperatures, they are most likely to denature. This means that their three-dimensional structure, especially the active site, is permanently damaged due to the breaking of weaker hydrogen and ionic bonds caused by increased kinetic energy and vibration. As a result, the enzymes lose their ability to bind to substrates and catalyze reactions, leading to a sharp decrease or complete loss of enzyme activity and a slower or halted reaction rate.

Explanation of enzyme response to temperature:

• At moderate temperatures, enzyme activity increases because molecules move faster, leading to more frequent and energetic collisions between enzymes and substrates.
• Beyond an optimum temperature, the enzyme's structure becomes unstable and begins to break down, causing denaturation.
• Denaturation disrupts the enzyme's active site, preventing substrate binding and thus stopping the enzyme's catalytic function.

Summary:

Exposure to very high temperatures causes enzymes to denature, permanently altering their structure and dramatically reducing or eliminating their catalytic activity.