7. Energy and Metabolism
Negative & Positive Feedback
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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 an 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 B using enzyme 1, 1, then molecule b into c using enzyme 2, c into d using enzyme 3, d into e using enzyme 4, and then e into the final product f using enzyme 5. 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 f and it wants to limit the production of product f, and so this can be when negative feedback can be very, very useful. And so with negative feedback, notice that the final product of this metabolic pathway is able to come back to an earlier step within the same metabolic pathway and inhibit 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 act 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 here 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.
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