Q21 / 180 · NEET 2015 (Phase 1) · Botany

Which one of the following statements is incorrect?

  • A
    A competitive inhibitor reacts reversibly with the enzyme to form an enzyme-inhibitor complex.
  • B
    In competitive inhibition, the inhibitor molecule is not chemically changed by the enzyme.
  • C
    The competitive inhibitor does not affect the rate of breakdown of the enzyme-substrate complex.
  • Correct answer
    D
    The presence of the competitive inhibitor decreases the Km of the enzyme for the substrate.

Solution

Competitive inhibition is a form of enzyme inhibition where binding of the inhibitor to the active site on the enzyme prevents binding of the substrate and vice versa. The presence of a competitive inhibitor increases the Km constant of the enzyme (and not decrease), while it does not affect the Vmax. The competitive inhibitor binds at the active site, so decreases the affinity of the enzyme for its substrate, so Km constant increases. If substrate concentration is increased, inhibition overcomes and attains normal Vmax.

Figure

Hence, the correct answer is option: 'D'.

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