Negative & Positive Feedback - Video Tutorials & Practice Problems
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1
concept
Negative Feedback
Video duration:
2m
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Video transcript
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.
2
concept
Positive Feedback
Video duration:
2m
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Video transcript
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 to 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 is product f and product f notice is going backwards to stimulate an earlier step of the same metabolic pathway, essentially stimulating enzyme 1 here so that enzyme 1 is able to operate faster, even faster than it normally does, stimulating this enzyme. And so ultimately when the enzyme 1 is stimulated it's going to create more of product b, or molecule b here. And then ultimately, this is going to lead to even more of the final product f. And so if a cell is in a scenario where they want to create even more 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 more 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.
3
Problem
Problem
________ is when the product of a biochemical pathway activates the production of itself.
a) Negative feedback inhibition.
b) Positive feedback.
c) Substrate feedback inhibition.
d) Product feedback inhibition.
A
Negative feedback inhibition.
B
Positive feedback.
C
Substrate feedback inhibition.
D
Product feedback inhibition.
4
Problem
Problem
Which of the following is TRUE about feedback inhibition?
a) Feedback inhibition has no physiological importance.
b) Multiple products are required for feedback inhibition.
c) Feedback inhibition of a pathway can only be accomplished by the products of that pathway.
d) Feedback inhibition involves products binding to the active site to prevent enzyme activity.
A
Feedback inhibition has no physiological importance.
B
Multiple products are required for feedback inhibition.
C
Feedback inhibition of a pathway can only be accomplished by the products of that pathway.
D
Feedback inhibition involves products binding to the active site to prevent enzyme activity.