Which statement describes the observation that supported the prediction about boiling reducing enzyme activity?

• A. The boiled tube showed increased activity, supporting the prediction
• B. The boiled tube showed decreased activity, supporting the prediction
• C. The boiled tube showed no change
• D. The boiled tube was not included

Answer: (B)

Boiling a protein enzyme disrupts its delicate three‑dimensional shape, mainly by breaking noncovalent bonds that hold the active site in the correct geometry. When the enzyme is denatured, the active site can no longer bind the substrate efficiently, so the rate of reaction drops toward zero. If the prediction was that boiling would reduce enzyme activity, observing decreased activity in the boiled tube directly supports that idea because it shows heat has irreversibly inactivated the enzyme's catalytic function. The other possibilities—seeing increased activity or no change—would not align with denaturation: heat generally inactivates the enzyme, and any lack of change would suggest unusual heat stability or measurement issues.