Question

students investigated the activity of catalase, an enzyme that breaks down hydrogen peroxide, using samples of fresh liver.

• in trial 1, hydrogen peroxide was poured on a piece of raw liver, and vigorous bubbling was observed.
• in trial 2, hydrogen peroxide was poured on a piece of liver that had been boiled for 5 minutes, and no bubbling occurred.

which conclusion is best supported by these observations?
a boiling the liver had no effect on catalase, so the reaction occurred normally.
b boiling the liver destroyed the catalase enzyme, preventing hydrogen peroxide from breaking down.
c boiling the liver caused hydrogen peroxide to evaporate before a reaction could take place.
d boiling the liver turned hydrogen peroxide into oxygen directly, so no catalase was needed.

Explanation:

Enzymes like catalase are proteins. High temperatures (such as boiling) denature proteins, changing their structure. When the liver was boiled (Trial 2), the catalase enzyme in it was destroyed (denatured). In Trial 1 (raw liver, no boiling), catalase was active and broke down hydrogen peroxide (hence bubbling - oxygen production). In Trial 2 (boiled liver), since catalase was destroyed (denatured by boiling), hydrogen peroxide could not be broken down (no bubbling).

Answer:

B. Boiling the liver destroyed the catalase enzyme, preventing hydrogen peroxide from breaking down.