Chemistry Macromolecules / Biochemistry ETEA 2024
PMDC Verified Question 3 of 47
In competitive inhibition, the inhibitor
A
Competes with enzyme
B
Binds with substrate
C
Irreversibly binds with enzyme
D
Competes with substrate
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Competes with substrate
Concept:

In competitive inhibition, the inhibitor possesses a molecular geometry and charge distribution closely resembling the natural substrate.

Solution:

  • Because of structural similarity, the inhibitor competes with the substrate for occupancy of the enzyme's catalytic active site.
  • When the inhibitor occupies the active site, the actual substrate is prevented from binding, forming an Enzyme-Inhibitor (\(\text{EI}\)) complex.
  • Competitive inhibition is reversible and can be overcome by increasing substrate concentration (\([S]\)), which increases \(K_m\) while keeping \(V_{max}\) unchanged.
  • Therefore, the inhibitor competes with substrate.


Why other options are incorrect:

  • A (Competes with enzyme): Incorrect; the inhibitor binds to the enzyme rather than competing against it.
  • B (Binds with substrate): The inhibitor interacts directly with the enzyme's active site, not with the substrate.
  • C (Irreversibly binds with enzyme): Competitive inhibition is reversible via mass action; irreversible inhibitors bind permanently via covalent bonds (e.g., nerve gases, cyanide).

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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