Negative & Positive Feedback

in this video, we're going to begin our lesson on negative and positive feedback by starting off with negative feedback. And so negative feedback is when the final product of a metabolic pathway inhibits an earlier step of the same exact pathway. And so because negative feedback inhibits and earlier step in the same exact pathway, really negative feedback is kind of acting like the red light to inhibit the metabolic pathway. And so, just like at a red light, when you're in a car, you need to stop or slow down with negative feedback. It's going to stop or slow down the metabolic pathway, and so notice over here on the right hand side, we're showing you an example of negative feedback occurring within a metabolic pathway. And so notice that this metabolic pathway converts molecule a into molecule, be using enzyme one, then molecule B and a C using enzyme to see and to de using enzyme three D and two d, using enzyme four and then e into the final product F using enzyme five. And so perhaps the cell is using this metabolic pathway to create product F, the final product. However, maybe the cell does not want to create too much of product EP, and it wants toe limit the production of product F. And so this can be when negative feedback can be very, very useful. And so, with negative feedback, noticed that the final product of this metabolic pathway is able to come back to an earlier step within the same metabolic pathway and inhibits an enzyme in the same metabolic pathway. And so the little negative sign that you see here is going to be used to represent inhibition, essentially blocking or slowing down the enzyme to prevent the conversion of molecule A into molecule B, and so by inhibiting an earlier step in the same pathway. Ultimately, that is going to lead to the decreased production of the final product. And so it's actually acting to inhibit the entire metabolic pathway. And so negative feedback is acting like the red light to this metabolic pathway to stop the metabolic pathway or inhibit the metabolic pathway and limit the production of the final product. And so this year concludes our introduction to negative feedback, and we'll be able to compare this to positive feedback in our next video. So I'll see you all there

So now that we've introduced negative feedback in our last lesson video in this video, we're going to introduce positive feedback, which is pretty much the exact opposite of negative feedback. And that's because positive feedback is when the final product of a metabolic pathway stimulates an earlier step in the same metabolic pathway. And so because positive feedback stimulates an earlier step in the same pathway, positive feedback pretty much acts like the green light toe further stimulate metabolic pathways. And so notice down below. We're showing you an image of a green light, and so, just like when you're driving, the green light represents stimulation of your car, where your car is going to accelerate and speed up. The positive feedback here is going to act like the green light for metabolic pathways and so notice here in this metabolic pathway, the final product, this product F and product F notices going backwards to stimulate an earlier step of the same metabolic pathway, essentially stimulating enzyme one here. So the enzyme one is able to operate faster, even faster than it normally does, stimulating this enzyme, and so ultimately, when the enzyme one is stimulated, it's going to create mawr of product beat. Oh, our, uh, molecule be here and then ultimately, uh, this is going to lead to even mawr of the final product f. And so if a cell is in a scenario where they want to create even mawr of the final product of a metabolic pathway, then that is when positive feedback can be very, very useful to the cell. Because positive feedback acts like the green light to the entire metabolic pathway, allowing even mawr of the final product f to be made. And so the positive sign that you see here the plus represents the stimulation of the enzyme here. And so this here concludes our introduction to positive feedback and we'll be able to get some practice applying the concepts that we've learned in our next few videos, so I'll see you all there.