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MCAT Biology – Substrate Concentrations

  • by Kerry Goldstein
  • Feb 20, 2015
  • MCAT Biology, MCAT Blog, MCAT Question of the Day

Noncompetitive inhibition differs from uncompetitive inhibition in that a noncompetitive inhibitor binds to an allosteric site on the enzyme and prevents it from catalyzing a reaction, whereas uncompetitive inhibitors bind to the enzyme-substrate complex and prevent catalysis. Increasing the substrate concentration would have which of the following effects?

A) Increasing impact of uncompetitive inhibitor and decreasing concentration of noncompetitive inhibitor

B) Decreasing impact of uncompetitive inhibitor and increasing impact of noncompetitive inhibitor.

C) Increasing impact of uncompetitive inhibitor

D) No effect

Explanation

A) Increasing impact of uncompetitive inhibitor and decreasing concentration of noncompetitive inhibitor

B) Decreasing impact of uncompetitive inhibitor and increasing impact of noncompetitive inhibitor.

C) Increasing impact of uncompetitive inhibitor

D) No effect

As substrate concentration increases, there will be more binding between the substrate and the enzyme. More enzyme-substrate complex in solution means more opportunity for an uncompetitive inhibitor to bind. Thus, as substrate concentration increases, the impact of an uncompetitive inhibitor would be expected to increase.

A: The concentration of a noncompetitive inhibitor isn’t changed by changing the substrate concentration.

B, D: As discussed above, the impact of an uncompetitive inhibitor would be increased.

 

 

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