Enzyme Inhibition - Video Tutorials & Practice Problems

Enzyme Inhibition

In this video, we're going to introduce enzyme inhibition and so recall that enzymes are all about speeding up chemical reactions. But sometimes the reactions might be going too fast, and the cell might need to stop the enzyme from going so fast. And so in that case, this is where enzyme inhibition can be useful. And so enzyme inhibitors are defined as compounds that interfere with and selectively inhibit the Potala sis of specific enzymes. And so enzyme inhibitors can be used to slow down enzymes if they're going too fast. Now, really, there are two types of inhibitors that we're going to introduce here in this video, and those two types are listed down below. And so the first type are the competitive inhibitors, and the second type that we're gonna introduce our noncompetitive inhibitors now competitive inhibitors, as their name implies, with the competitive part, they are going to compete with the substrate for a position in the free enzymes active site. And so competitive inhibitors can Onley bind to the enzyme when the active site is actually free. And so it's the substrate and the competitive inhibitor that are going to compete with each other for a binding spot in the active site of the inside. So let's take a look at our image down below, over here, on the left hand side, at competitive inhibition, and so notice that the enzyme once again is shown in red and and blue. What we're showing you is the competitive inhibitor, and it's called a competitive inhibitor because it's going to compete with the substrate over here, which is in black for a position in the enzymes active site. And so if the competitive inhibitor binds to the enzymes active site before the substrate does, then the competitive inhibitor is going to block the substrate from binding to the active site, as we can see over here. And so notice that the competitive inhibitor is binding to the active side of the enzyme, and when it binds to the active side of the enzyme, it is preventing the normal substrate from binding. And if the normal substrate cannot bind, then that means that Catala sis is going to be prevented and the enzymes reaction is going to essentially slow down and be inhibited. And so the second type of inhibitor that we're going to talk about our noncompetitive inhibitors, and as their name implies, they are non competitive, so they do not compete with the substrate for ah, position in the active site. Instead, the noncompetitive inhibitors going to bind to what's known as an aloe stare IQ site. And so theologian Eric site on an enzyme, is defined as an alternative site for an inhibitor binding that is not going to be the active site. And so let's take a look at our image down below over here on the right hand side to get a better understanding of noncompetitive inhibition. And so notice that the noncompetitive inhibitors shown here and purple so we can go ahead and label as the non competitive inhibitor. And so the noncompetitive inhibitor notice is not going to compete with the substrate over here for a binding position in the active site. Instead, the noncompetitive inhibitor is going to buy into a completely different site over here that we have in blue, and this site is referred to as the alot Stare IQ site. And so when an inhibitor binds to the Alice Derek site off an enzyme, it can cause the enzyme to change its shape to alter its shape and so when it alters its shape, its going toe also alter the shape of the active site. And so notice that the active site here is taking on a different shape than what it used to have before the noncompetitive inhibitor bound. And so the active site will change in such a way that it will prevent these substrate from binding to the enzyme. And so, if the substrate cannot bind to the enzyme, then that is going to prevent or inhibit catalysis and slow down the enzyme. And so, basically, these inhibitors can be used to slow down and inhibit enzymes. And so this year concludes our introduction to enzyme inhibition as well as the competitive and noncompetitive inhibitors, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

Which of the following statements correctly describes competitive inhibition?

a) A competitive inhibitor binds to the substrate and inhibits it from binding to the active site of the enzyme.

b) A competitive inhibitor binds to a site other than the active site and inhibits the substrate from binding.

c) A competitive inhibitor binds to the active site and degrades the enzyme.

d) A competitive inhibitor binds to the active site of an enzyme and inhibits the substrate to bind.

• A. A competitive inhibitor binds to the substrate and inhibits it from binding to the active site of the enzyme.
• B. A competitive inhibitor binds to a site other than the active site and inhibits the substrate from binding.
• C. A competitive inhibitor binds to the active site and degrades the enzyme.
• D. A competitive inhibitor binds to the active site of an enzyme and inhibits the substrate to bind.

How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction?

a) By binding to the active site of the enzyme, thus preventing binding of the normal substrate.

b) By binding to an allosteric site, thus changing the shape of the active site of the enzyme.

c) By decreasing the free-energy change of the reaction catalyzed by the enzyme.

d) By binding to the substrate, thus changing its shape so that it no longer binds to the active site of the enzyme.

• A. By binding to the active site of the enzyme, thus preventing binding of the normal substrate.
• B. By binding to an allosteric site, thus changing the shape of the active site of the enzyme.
• C. By decreasing the free-energy change of the reaction catalyzed by the enzyme.
• D. By binding to the substrate, thus changing its shape so that it no longer binds to the active site of the enzyme.

Which of the following types of enzyme inhibition is overcome by increasing the substrate concentration?

a) The need for a coenzyme.

b) Noncompetitive inhibition.

c) Competitive inhibition.

d) None of the above.

• A. The need for a coenzyme.
• B. Noncompetitive inhibition.
• C. Competitive inhibition.
• D. None of the above.