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Multiple Choice
Which of the following is not true for a competitive inhibitor in enzyme-catalyzed reactions?
A
It can be overcome by increasing substrate concentration.
B
It binds to the active site of the enzyme.
C
It decreases the maximum velocity (Vmax) of the reaction.
D
It increases the apparent Km of the substrate.
Verified step by step guidance
1
Understand the role of a competitive inhibitor: A competitive inhibitor competes with the substrate for binding to the active site of the enzyme. This means it can be outcompeted by increasing the concentration of the substrate.
Analyze the effect on Vmax: In competitive inhibition, the maximum velocity (Vmax) of the reaction remains unchanged because the inhibitor can be outcompeted by a high concentration of substrate, allowing the enzyme to reach its maximum rate.
Consider the effect on Km: Competitive inhibitors increase the apparent Km of the substrate. This is because a higher concentration of substrate is needed to reach half of Vmax, indicating a decrease in the enzyme's affinity for the substrate.
Evaluate the statement about Vmax: The statement 'It decreases the maximum velocity (Vmax) of the reaction' is incorrect for competitive inhibitors, as Vmax remains the same.
Conclude which statement is not true: Based on the analysis, the statement that a competitive inhibitor decreases Vmax is not true, as competitive inhibition affects Km but not Vmax.