Enzyme Catalysis

AP Biology· difficulty 3/5

A student investigates catalase using filter paper disks soaked in liver extract dropped into 3% H2O2 at 5, 20, 35, 50, and 65 degrees Celsius. Reaction rate (1/rise time, in s^-1) is calculated from triplicate trials. The graph below summarizes the results.

Temperature (C) Rate (1/s) 5 20 35 50 65

Which conclusion is best supported by the data?

  • A

    Catalase activity peaks near 35 C and declines at higher temperatures due to denaturation

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  • B

    Temperature has no measurable effect on catalase activity

  • C

    Catalase is most active at 65 C

  • D

    Catalase activity increases linearly with temperature across the entire range

Explanation

The rate rises from 5 to 35 C, peaks near body temperature, then falls at 50 and 65 C. The decline at high temperature is consistent with denaturation of the enzyme's active site, which destroys catalytic function.

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