Summary
An inhibitor resembling the substrate binds the active site and can be overcome by more substrate.
In depth
The inhibitor competes with the substrate for the active site, so Km appears to increase while Vmax stays the same. High substrate concentration can outcompete it.
Many drugs act this way.
Competitive inhibitors often resemble the substrate: malonate inhibits succinate dehydrogenase, methotrexate resembles folate and blocks DHFR in cancer cells, and ethanol is used as a treatment for methanol poisoning because it competes for alcohol dehydrogenase, slowing production of toxic formaldehyde and formic acid.
On a Lineweaver-Burk plot, lines for different inhibitor concentrations meet on the y-axis because Vmax is unchanged, while the x-intercept moves.
Frequently asked questions
What is Competitive Inhibition?
An inhibitor resembling the substrate binds the active site and can be overcome by more substrate.
Which area of biology covers Competitive Inhibition, and how advanced is it?
Competitive Inhibition is one of the 51 topics in Biomolecules & Biochemistry. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Noncompetitive Inhibition, Active Site, Michaelis-Menten Kinetics.
Why does Competitive Inhibition matter?
Antibiotics such as sulfonamides compete with PABA in bacterial folate synthesis, which human cells do not carry out.
Can you give an example of Competitive Inhibition?
Statins resemble HMG-CoA and inhibit cholesterol synthesis; methotrexate competes for dihydrofolate reductase.
What should I learn before Competitive Inhibition?
Work through the Beginner topics in Biomolecules & Biochemistry first, such as Water Properties, Carbon Chemistry, Carbohydrates, then return to Competitive Inhibition. Intermediate topics assume the Beginner vocabulary.
What topics are related to Competitive Inhibition?
The closest topics to Competitive Inhibition are Noncompetitive Inhibition, Active Site, Michaelis-Menten Kinetics, Steroids. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Competitive Inhibition?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Competitive Inhibition. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is Competitive Inhibition different from Noncompetitive Inhibition?
Competitive Inhibition: An inhibitor resembling the substrate binds the active site and can be overcome by more substrate. Noncompetitive Inhibition: An inhibitor binds elsewhere on the enzyme, lowering Vmax without changing Km. Read both side by side and note what each one explains.
How should I study Competitive Inhibition step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Noncompetitive Inhibition and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.