Enzyme-Substrate Complex - Video Tutorials & Practice Problems
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concept
Enzyme-Substrate Complex
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3m
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Video transcript
In this video, we're gonna talk about the enzyme substrate complex. So the enzyme substrate complex is commonly abbreviated with the capital letters e s, and we're gonna see that a lot moving forward throughout our course as well. And so the idea or the concept of an enzyme substrate complex is actually really straightforward. It's literally just an intermediate that forms when the enzyme binds to its substrate. So pretty easy. Right? And so recall from your previous chemistry courses that intermediates are transient molecules because they don't last very long before they react again. And on an energy diagram, these intermediates appear at the local minimum energy points within a multi step reaction. And so it's really important not to confuse intermediates with transition states, which we covered in our last lesson video. And so recall that transition states appear at the local maximum peak energy point. However, intermediates appear at the local minimum energy points. And so if you're having some difficulty visualizing the difference between transition states and intermediates, then hang on tight because in our next example video, we'll show you guys an example of what this looks like. Now, down below here, what we're showing is a typical enzyme catalyzed reaction where we have an enzyme, which is commonly abbreviated with the letter e, and a substrate, which is commonly abbreviated with the letter s. And then we know that the enzyme can form a complex with the substrate, known as the enzyme substrate complex. And then, of course, the enzyme is able to convert the substrate into the product, which is commonly abbreviated with the letter p. And then the enzyme is not consumed in the reaction, so it takes on the original form that it had before the reaction even started. And so the next thing that I want you guys to know in this video, is that the interactions that allow the enzyme to form a complex with the substrate are predominantly mediated by non covalent forces, such as hydrogen bonds and ionic bonds, for example. But that's not to say that covalent bonds never form in the enzyme substrate complex while catalysis is occurring, because they actually can occur, and we'll talk about that more when we talk about different types of enzyme catalysis later in our course. But for now, all I want you guys to know is that the majority of the interactions in the enzyme substrate complex are non covalent forces. And so these weak non covalent forces that form between the enzyme and the substrate in the enzyme substrate complex actually provide the driving force for enzyme catalysis. And we'll be able to talk about this even more in our next lesson video. So I'm excited to see you guys in the next video. See you guys there.
2
example
Enzyme-Substrate Complex Example 1
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Video transcript
Alright, so here's an example problem that's going to help us visualize the difference between transition states and intermediates. And the example problem wants us to appropriately label the arrows in the reaction energy diagram below using the provided terms over here on the left. And notice that the energy diagram has the free energy on the y axis and the reaction coordinate or the time that passes as the reaction progresses on the x axis. And we know that every reaction begins with reactants, and so this arrow pointing to the very beginning of our curve is gonna correspond with the reactants, and the reactants of an enzyme catalyzed reaction are known as substrates, which is option c here. So we can go ahead and label this arrow right here with option c, and then cross it off our list. So we also know that every reaction ends with products, and so this arrow here pointing to the end of our curve corresponds with the products, which is option a. So we can go ahead and label it with option a, and then cross it off our list. And so the remaining three arrows that we have here correspond to either transition states or intermediates. And so recall from our previous lesson video that intermediates appear at the local minimum energy points. And so, notice that this arrow here is pointing to a local minimum energy point because it's showing up at the bottom of this valley here. And so because it's showing up at a local minimum energy point, this is an intermediate, which is option B, and we can label this arrow with option B, and then cross it off our list. And so, both of these arrows up here are both pointing to local maximum energy points because they are showing up at the top of a hill. And so, because they're showing up at local maximum energy points, we know that these are both transition states. So we can put the double dagger symbol here to show that these are both transition states. Now, notice that the provided terms over here have 2 different transition states. We have a non rate limiting transition state, and then we have a rate limiting transition state. So recall from your previous chemistry courses that rate limiting just means slow, and we already know that slow reactions have a large energy of activation. And so if we look at this first transition state here, And so if we look at this first transition state here, the energy of activation is going to be the difference in energy from the substrate to the transition state, and so it'll be this energy barrier right here. Now if we look at the energy of activation for the second transition state over here, it's gonna be the, difference in energy between its substrate, which would be the intermediate here, and this other transition state. So essentially, it's just going to be this little energy of activation. And so because this first transition state has a much larger energy of activation with this green bar here, in comparison to the second one, This, larger one, has a larger energy of activation, so it's going to be slower and it's going to be the rate limiting transition state. So we can go ahead and label, this one with option e, and then of course, we can cross that off, and the remaining one over here is gonna be option d, and we can cross that off. So that concludes this example problem, and I'll see you guys in our next video.
3
concept
Enzyme-Substrate Complex
Video duration:
5m
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Video transcript
So in our last lesson video, we said that the interactions between the enzyme and the substrate in the enzyme substrate complex predominantly consist of non covalent forces. And when these non covalent forces form between the enzyme and the substrate, can be abbreviated with the symbol delta g b, and the quantity of binding energy is defined as the energy difference between the uncatalyzed and the catalyzed transition states. And again, binding energy is derived from the release of free energy when non covalent interactions form in the enzyme substrate complex. Now later in our course, we're gonna talk about the exact factors that enzymes influence by utilizing the released binding energy in order by utilizing the released binding energy in order to stabilize the transition state in the active site. And so essentially, the main takeaway is that the way that enzymes lower the energy of activation is by stabilizing the transition state. And really, that's the major takeaway from this video. So down below in our example image, notice on the far left here, we have the same image that we have up above in our previous lesson video. And so we know that the enzyme and the substrate are able to interact with each other to form the enzyme substrate complex. And the enzyme is able to interact with the substrate in such a way to catalyze the reaction and make the products appear at a faster rate. And the enzyme is released unaltered without being consumed by the reaction. So it's in the same exact state as it was before the reaction took place. And so over here on the right, what we have is a energy reaction diagram, and you can see that the uncatalyzed reaction is being shown as a dotted line, so you can see that the transition state for the uncatalyzed reaction is really, really high. And unlike our previous reaction energy diagrams, notice that the enzyme catalyzed curve is actually showing the formation of the enzyme substrate complex intermediate here, And that's something that was not shown in our previous energy diagrams. And what you'll probably find is that in most energy diagrams, the enzyme substrate complex is not going to be shown. And the reason for that is because, remember, the enzyme substrate complex is an intermediate. So it's a transient molecule that does not last very long. So we don't typically focus most of our attention on it. So to simplify the enzyme catalyzed curves, a lot of times, the enzyme substrate complex is just simply not shown. But here, we're showing the formation of the enzyme substrate complex to show a more realistic depiction of an enzyme catalyzed reaction. But moving forward, what you'll probably see is that the enzyme substrate, reactions are gonna be shown without showing the enzyme substrate complex. But here, what you'll notice is that there is a little bit of an energy of activation for the formation of the enzyme substrate complex, but it's so small that it's not really an issue and it's able to form pretty readily. Now what you should notice here is that the enzyme catalyzed reaction has a much lowered energy of activation here for the transition state that corresponds with the formation of the products. And so we said earlier in our lesson that binding energy, the quantity of binding energy, is defined as the energy difference between the uncatalyzed and the catalyzed transition states. So again, the uncatalyzed transition state is going to be the transition state that corresponds with the local maximum peak energy point for the uncatalyzed curve. And the catalyzed transition state is going to correspond with the local maximum peak energy point for the catalyzed enzyme catalyzed curve. And so essentially, the binding energy is defined as this green area that's shown here, that's the difference between these two transition states that correspond with each other. And so this binding energy is symbolized with delta g b. And again, it's this green area here with the energy difference of these two transition states. And again, what you'll notice is that it's this binding energy that's utilized to stabilize the transition state and essentially lower the energy of the transition state. And once the transition state energy is lowered and stabilized, the reaction is able to proceed at a faster rate, and that's exactly how enzymes, speed up chemical reactions, is by utilizing binding energy to stabilize the transition state. And again, that's the major takeaway of this video. So we'll we'll be able to utilize some of these concepts in our next video, so I'll see you guys there.
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Problem
Problem
What can the binding energy (ΔGB) of an enzyme catalyzed reaction tell us?
A
The change in the rate/speed of the reaction.
B
The change in the equilibrium constant (Keq) of the reaction.
C
The change in the reaction EA between the catalyzed & uncatalyzed transition states.
D
a & c.
E
All options are true.
5
Problem
Problem
Which is the best definition of binding energy regarding enzyme catalysis?
A
Energy absorbed by the enzyme upon its binding to the substrate.
B
Energy released by interactions between the enzyme's active site & substrate.
C
Energy released by the products of an enzyme.
D
The difference in energy between the substrates & products.