GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Enzyme Mechanics

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

Example Question #2 : Enzymes

Which of the following best describes when an inhibitor binds an enzyme at a separate site from the active site, but only when the enzyme and substrate are already bound in complex?

Possible Answers:

Competitive inhibition 

Uncompetitive inhibition

Non-competitive inhibition 

Allostery 

Reversible inhibition

Correct answer:

Uncompetitive inhibition

Explanation:

The correct answer is uncompetitive inhibition. The formation of a enzyme-substrate complex creates an alternative site on the enzyme for an inhibitor to bind. This mechanism is considered uncompetitive because the inhibitor and substrate are not competing for the same binding site on the enzyme. 

Example Question #3 : Enzymes

What is the primary mechanism by how enzymes increase the rate of a reaction?

Possible Answers:

They lower the activation energy needed in the reaction.

They decrease the stability of the transition state.

They decrease the reverse reaction rate and increase the forward reaction rate.

They decrease the internal energy of the final product.

Correct answer:

They lower the activation energy needed in the reaction.

Explanation:

Enzymes exert their effect on the reaction rate by decreasing the energy needed for the reaction to proceed. As a result, the enzyme will decrease the activation energy. It should be noted that the forward reaction rate and reverse reaction rate are both increased by an enzyme. If this were not the case, more product would be made compared to the uncatalyzed reaction, and enzymes do not affect equilibrium constants for reactions.

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
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