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Biochemistry

Learn the toughest concepts covered in Biochemistry with step-by-step video tutorials and practice problems by world-class tutors

7. Enzyme Inhibition and Regulation

Negative Feedback

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concept

Negative Feedback

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In this video, we're going to introduce yet another way that cells can regulate their biochemical reactions, and that is through negative feedback. And so negative feedback is also sometimes referred to as just feedback inhibition. And so negative feedback or feedback. Inhibition is an efficient and a very common means for biochemical regulation, and so cells use negative feedback all the time to regulate their reactions. Now, really, the purpose of negative feedback is to prevent the over production as well as the wasteful production of a product. And so as we'll see moving forward, negative feedback is really just a way for molecules, such as a product to regulate the production of its own activity. And so negative feedback inhibition is when the final product or just ah later product in a metabolic pathway can come back and inhibit an earlier step in the same exact metabolic pathway that led to that products production. And so ultimately this is going to slow down, uh, the entire metabolic pathway, and that is going to begin to decrease the final concentration of that product that acted to inhibit the reaction. And so as we'll see down below, in our example uh, negative feedback inhibitors really do, uh, inhibitors really do act as inhibitors and recall that inhibitors are commonly represented with a negative symbol. And so these negative feedback inhibitors are going to bind to an Alice, Terek and Allah host Eric site on the A list Eric Enzyme. And of course, that means that it's not going to bind to the enzymes active site and so down below. In our example notice, we're saying that negative feedback inhibition really acts like the red light to inhibit metabolic pathways. And so, over here, what we have is a red light to show you that really negative feedback acts like a red light and slows down these metabolic pathways. And so, over here we're showing you an example of a metabolic pathway, and so you can see that we have all of these reactions here and notice that most of these reactions are being catalyzed by Michalis mention enzymes. But here we do have one enzyme that is displaying Alistair kinetics. And so notice here that we have a final product. Af And, uh, if the concentration of F happens to get way too high, then f can actually come back and inhibit the Alice Derek Enzyme number one here. And we know that it's inhibiting because again, we have a minus sign here that represents inhibition. And so if F comes all the way back to inhibit enzyme number one, then that's going to prevent the conversion from A to B, and ultimately, that's going to lead to the decrease of the concentration of product F. And so when the final concentration of the product F over here is returned back to normal or lower levels, then the feedback inhibition that is caused by product F here is essentially going to stop. And that's going to allow the metabolic pathway to proceed once again. And so clearly here we're talking about negative feedback inhibition, and you can see how, really, through negative feedback inhibition. Molecules such as product F here are able to regulate its own production. And so, by coming back in inhibiting enzyme number one, uh, product F can, uh, influence the decrease or the lowering of it's a concentration. And so it turns out again that negative feed bank, um, inhibition is an efficient and a common means for biochemical regulations. So later, in our course, we're going to talk about many different examples of negative feedback, and in our next lesson, video will specifically talk about one particular example. And so I'll see you guys in that video.
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example

Negative Feedback Example 1

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So now that we've covered the basics of negative feedback or feedback inhibition in this video, we're going to cover an example of feedback regulation in glide colle assists. And so recall from your previous biology courses that glide colle assists is just a process in cellular respiration that breaks down glucose in order to generate energy in the form of ATP. And so notice down below in our image, we're showing you a little snippet of the glide. Collis is process or metabolic pathway and over here on the far left notice, we're starting with a glucose molecule. And of course, one of the final products of glide Collis iss is the net generation of ATP. And so again, we're not showing you the full light, callous iss uh, metabolic pathway here. But we will cover the full glide callouses metabolic pathway later in our course. For now, we just want to emphasize this idea of feedback Regulation in Glen Collis is, and so imagine a scenario where the cell already has plenty of ATP. And so in that scenario, the cell would not want to be breaking down glucose to generate even mawr ATP. And so in this scenario, a teepee can actually act as a negative feedback regulator to inhibit one of the enzymes that acting like Hollis is. And this enzyme is known as phosphor. Oh, fruit token is abbreviated as p f K and phosphate fruit tokens or P. F. K is an Alice Derek Enzymes. That catalyze is a particular reaction. And like Collis is, and if we take a look down below noticed that p f k catalyze is the conversion of fructose six phosphate right here into fructose 16 biss phosphate right here, essentially adding an extra phosphate group right here at this position. And so it needs to utilize a teepee here as a co substrate in order Thio convert. Uh, this reaction right here catalyzed this reaction. And so again, p f k phosphor fruit token is is going to be regulated via negative feedback by a teepee. And so eight eep can come back and essentially negatively regulate uh, p f k in order to, uh, inhibit P f K and essentially lead to the decrease of a teepee or prevent the production of ATP. And so because a teepee is also utilized as a co substrate for P, f K and a teepee also acts as a negative. Alice Terek, regulator of P f. K. That actually makes a t p a Homo Tropic Alice, Terek Effect ER And again, that's because 80 p is used as a substrate as well as analysis. Eric Effect er And because the substrate is the same as the Alice Derek Effect er, that makes the Alice Derek effect er, homo tropic. And so again, this is just one example of negative feedback in glide calluses. But later in our course, we'll talk about ah lot Mawr examples of negative feedback throughout all of cellular respiration. But for now, this concludes our example of feedback regulation in Glen Collis ISS, and our next video will be able to get some practice utilizing the concepts that we've learned. So I'll see you guys in that video.
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Problem

The scheme below represents a hypothetical metabolic pathway for the synthesis of compound Y. The pathway is regulated by feedback inhibition. If S → T is the rate-limiting step, circle what the most likely inhibitor is and indicate with an arrow where the inhibition most likely occurs:

S → T → U → V → W → X → Y

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Problem

Which of the following is TRUE about feedback inhibition?

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