Positive Feedback

So now that we've covered negative feedback in this video, we're going to introduce the opposite type of feedback regulation, which is positive feedback. So with positive feedback, it turns out that the final product of a metabolic pathway instead of inhibiting an earlier step, it actually activates or stimulates an earlier step in the same exact metabolic pathway. And so again, with positive feedback, the final product is going to act as an activator to again further stimulate the production and the build up of the final product. And so, in our example, down below notice, we're saying that positive feedback really acts like the green light to activate or stimulate metabolic pathways. And so over here, notice that we have this green light to remind you that positive feedback access the green light to allow metabolic pathways to proceed faster. And so notice Here we have our metabolic pathway. And again, most of the enzymes in our metabolic pathway display McHale s mention kinetics. However, we do have one enzyme here enzyme one that is analysis Derek enzyme and displays Alistair Kinetics and so notice. Here we have product f that's able to come back in this pathway and it's able to stimulate or activate, uh, enzyme number one. So the enzyme number one essentially increases its initial reaction rate, and it converts, uh, reacted a into intermediate, be here of faster, and that ultimately leads to the increase in the concentration of product F. And so you can imagine a scenario where product F uh in a cell needs to be maintained at high levels in order for the cell to survive. And so, in order for F to ensure that its concentration is maintained at high levels, AF can act as a positive feedback regulator for the enzyme number one to constantly stimulate it so that it gives this metabolic pathway to green light to continue to produce f so that f is maintained at those high concentrations that's required for survival. And again, this is our example of positive feedback. And so this here concludes our introduction to positive feedback and in our next couple of videos will be able to get some practice. So I'll see you guys there

so now that we've covered both positive and negative feedback regulation in this video, we're going to introduce the idea of metabolic pathway communication. And so it's actually pretty common within cells for metabolic pathways to communicate or interact with each other through these feedback regulation mechanisms that we already covered in our previous lesson videos, including negative and positive feedback. Now, really, the main purpose of this biological communication or interaction between metabolic pathways is to ensure efficient production of a single final product. And so what's important to note as we move forward with our lesson of metabolic pathway communication is that some Alice Derek Enzymes can actually bind both Alice Terek activators as well as Alice Derek inhibitors. And this means that some Alice Terek enzymes are capable of supporting both positive as well as negative feedback, and we'll be able to see some examples of that down below in our image. Now, it's also important to note that the same molecule could potentially act as both an activator for one Alice Terek enzyme and an inhibitor for a different Alice Terek enzyme. And again, we're going to see examples of that down below in our image now taking a look at our image down below. At first glance, it looks pretty darn complicated, but it's definitely not as complicated as it looks. And if you take a closer look, notice that we're showing you on Lee three different metabolic pathways. So we have metabolic pathway number one here with this light blue background. Then we have metabolic pathway number two here with this yellow background, and we have metabolic pathway number three over here with this pink background. And what's important to note is that these three metabolic pathways can actually communicate with each other in order to again ensure efficient production of a single final product. And that single final product in this, uh, image here is going to be product kay, which is all the way over here on the right. And so what's also important to note is that within a cell there's actually hundreds or thousands of metabolic pathways, and here in this image were on Lee showing you three metabolic pathways and so within a cell. It's possible, for ah, lot of these metabolic pathways to communicate with each other, and they can communicate with each other in different ways. So here. We're only showing you one example of how, uh these metabolic pathways could potentially communicate. And so what's really important to note is that the final product of Pathway number one here is actually molecule number or molecule f here, and the final product of Pathway number two is a molecule. I and so molecules I and molecule f uh must actually interact with each other, uh, in order for pathway three to proceed. And, uh, Pathway three is the one to directly form the final product of interest, which is again product uh, molecule K here. And so what I want you guys to notice is that the final product of pathway number One notice that it can actually act as both an inhibitor to enzyme number one. But it can also act as an activator two enzyme number six in a different pathway. And so this is what we mean by metabolic pathway communication. Because the product of pathway number one is capable of acting as an al hysteric effect er for an enzyme in a different pathway, that is what we mean by communication or interaction between these metabolic pathways. And so you can imagine a scenario where product F is at very, very, very high concentrations. Well, maybe those concentrations are simply too high. Well, in that scenario, product F can actually go back and act as an Alice Derek inhibitor to inhibit enzyme number one and therefore decrease the concentration of its itself. And so again, recall that the positive signs here are going to represent activators, whereas the negative signs are going to represent inhibitors. And so that's why you can see that product f here, a pathway number one can act as an inhibitor for enzyme number one. But again, imagine a scenario where the inhibitor I'm sorry, the final product of pathway number two here molecule I eyes at low concentrations. Well, under that, um, scenario, uh, this f here could act as an activator to enzyme six toe help increase the concentration off molecule I. And so there is also some communication between pathway number two with I and a pathway number one up here with enzyme number one. So it's noticed that molecule I hear can actually act as an activator for enzyme number one to help increase the concentration of F and so you can see how there is this communication between these different pathways now? Also notice that pathway number three the final product here, can act as an inhibitor four enzyme number one as well as a nen hih bitter for enzyme number six. And so, uh, the concentration of K here can also regulate, uh, its own activity through negative feedback because it is inhibiting. And so any time you see a positive sign, that would represent a form of positive feedback through activation. And then any time you see a negative sign that would represent a negative feedback through, um, inhibitors. And so, essentially here this concludes our lesson on how metabolic pathways can actually communicate with one another. And and our next couple of videos we're going to get some practice interpreting these arrows and activators and inhibitors and the mechanism of communication between the pathways. And so this concludes our lesson, and I'll see you guys in our next video