Competitive Inhibition of Enzymes: Definition & Examples

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: What are Enzymes? - Definition & Explanation

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:00 Enzymes and Enzyme Function
  • 1:25 Regulation of Enzyme Function
  • 1:54 Competitive Inhibition
  • 3:42 Examples of…
  • 5:13 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed Audio mode

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Darla Reed

Darla has taught undergraduate Enzyme Kinetics and has a doctorate in Basic Medical Science

This lesson gives a brief overview of enzymes and enzyme function. It further defines competitive inhibition and provides real-life examples of competitive inhibitors.

Enzymes and Enzyme Function

What would be the quickest way to completely destroy a piece of paper? You could tear it up or shred it, but you'd still have pieces of it. You could dissolve it in water, but that might take a while. The fastest option (other than eating it) would probably be to burn it.

Cells like to have the fastest option when it comes to destroying, building, or changing molecules. Just as you would use fire to change the paper into ash as fast as possible, cells use enzymes to speed up the chemical reactions that change molecules.

Let's take a look at how this works and get some basic terminology down. Using our example of burning paper, the thing that is being changed (the paper) is called a substrate. The place on the enzyme where the substrate attaches to and gets changed (the flame) is called the active site, and the final result (ash) is called a product. A real-life example of this is pepsin, which is an enzyme that helps us digest the protein in food. Pepsin (the enzyme) breaks down proteins (the substrate) into peptide groups called polypeptides (the product). Without the work of enzymes, such as pepsin, we wouldn't be able to live.

Enzymes use substrates to make products

In the image, you can see that substrates fit into an active site kind of like a puzzle piece, and they need to fit into the right spot. If you are holding a candle, putting a piece of paper on the wax or under the candle won't burn it. It will only burn if you put it where the flame is.

Regulation of Enzyme Function

Now like the fire in our example above, enzymes need to be regulated because just as an out-of-control fire is dangerous to a house, out-of-control enzyme activity is dangerous to cells. Cells can regulate enzyme activity by activating or inhibiting their functions. Cells can inhibit enzyme activity by changing the form of the active site to stop substrate binding, stopping the formation of product after the substrate is bound, or allowing fake substrates to compete with real substrates.

Competitive Inhibition

This last option, allowing fake substrates to compete with real ones, is called competitive inhibition. Fake substrates competing with real substrates for the opportunity to bind at an active site (hence the name competitive) slows or stops enzyme function. Fake substrates look like real substrates to an enzyme's active site; they are, in essence, 'look-a-likes.' When a fake substrate binds to the active site of an enzyme, it can't be processed in the same way and it won't turn into a product. A fake substrate is called a competitive inhibitor. Competitive inhibitors bind the active site of an enzyme, preventing a real substrate from binding and a product from being formed.

Competitive inhibition can be overcome by addition of substrate, which increases an enzyme's chance of finding real substrate. Let's look at how this might work. Say you're trapped in a dark pen with a lion. Next to you is a tree trunk that has the same shape as you. If the lion mistakes the tree trunk for you and gets it stuck in its mouth, you are not turned into its next meal. The lion (enzyme) is inhibited from eating you (substrate) because the tree trunk (competitive inhibitor) is stuck in its mouth (active site). But, if we trap ten more people in with you, the lion (enzyme) has a much better chance of finding a person (substrate) instead of a tree trunk (competitive inhibitor).

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account