Biology 9700 · AS & A Level · Factors that affect enzyme action

Factors that affect enzyme action — practice question

The action of an enzyme can be influenced by a competitive inhibitor. Which row gives the correct effect of a competitive inhibitor on the value of $K_m$ and the reason for this?

  • Aeffect: increased; reason: Few substrate molecules will bind to the active site when the substrate concentration is low because the active site is blocked by the inhibitor.
  • Beffect: increased; reason: $V_{max}$ will increase because the substrate will only bind to the active site when the concentration of the substrate is high.
  • Ceffect: no effect; reason: At high substrate concentrations, substrate molecules are still able to bind to the enzymes in the presence of a competitive inhibitor.
  • Deffect: no effect; reason: The inhibitor molecule does not bind to the active site; it binds to a site on another part of the enzyme.

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