MCAT Biochemistry Question 30: Answer and Explanation

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Test Information

Question: 30

15. How does the ideal temperature for a reaction change with and without an enzyme catalyst?

  • A. The ideal temperature is generally higher with a catalyst than without.
  • B. The ideal temperature is generally lower with a catalyst than without.
  • C. The ideal temperature is characteristic of the reaction, not the enzyme.
  • D. No conclusion can be made without knowing the enzyme type.

Correct Answer: B

Explanation:

The rate of reaction increases with temperature because of the increased kinetic energy of the reactants, but reaches a peak temperature because the enzyme denatures with the disruption of hydrogen bonds at excessively high temperatures. In the absence of enzyme, this peak temperature is generally much hotter. Heating a reaction provides molecules with an increased chance of achieving the activation energy, but the enzyme catalyst would typically reduce activation energy. Keep in mind that thermodynamics and kinetics are not interchangeable, so we are not considering the impact of heat on the equilibrium position.

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