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Apparent Km and Vmax quiz

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  • What does the term 'apparent Km' refer to in enzyme kinetics?
    Apparent Km is the Michaelis constant measured in the presence of an inhibitor, reflecting altered substrate affinity.
  • How is 'apparent Vmax' defined?
    Apparent Vmax is the maximum reaction velocity of an enzyme in the presence of an inhibitor.
  • What effect does a competitive inhibitor have on apparent Km?
    Competitive inhibitors increase apparent Km, indicating weaker substrate binding.
  • Does a competitive inhibitor affect apparent Vmax?
    No, competitive inhibitors do not change apparent Vmax.
  • How does an uncompetitive inhibitor affect apparent Km?
    Uncompetitive inhibitors decrease apparent Km, resulting in stronger substrate binding.
  • What happens to apparent Vmax in the presence of an uncompetitive inhibitor?
    Apparent Vmax decreases with uncompetitive inhibitors, reducing the enzyme's maximum velocity.
  • What are the inhibition factors alpha (α) and alpha prime (α′)?
    Alpha (α) quantifies inhibition on the free enzyme, while alpha prime (α′) quantifies inhibition on the enzyme-substrate complex.
  • How is apparent Km calculated for competitive inhibition?
    Apparent Km for competitive inhibition is α × Km, where α ≥ 1.
  • How is apparent Km calculated for uncompetitive inhibition?
    Apparent Km for uncompetitive inhibition is Km divided by α′, where α′ ≥ 1.
  • How is apparent Vmax calculated for uncompetitive inhibition?
    Apparent Vmax for uncompetitive inhibition is Vmax divided by α′.
  • How do mixed and noncompetitive inhibitors affect apparent Km?
    Mixed and noncompetitive inhibitors can increase or decrease apparent Km, depending on the values of α and α′.
  • How do mixed and noncompetitive inhibitors affect apparent Vmax?
    Apparent Vmax decreases for both mixed and noncompetitive inhibitors, as it is divided by α′.
  • What does an increased apparent Km indicate about substrate affinity?
    An increased apparent Km means the enzyme has weaker affinity for the substrate.
  • What does a decreased apparent Km indicate about substrate affinity?
    A decreased apparent Km means the enzyme has stronger affinity for the substrate.
  • Why is understanding apparent Km and Vmax important in enzyme kinetics?
    It helps interpret how inhibitors affect enzyme activity and catalytic efficiency.