Enzyme-Substrate Complex

in this video, we're going to talk about the enzyme substrate complex, so the enzyme substrate complex is commonly abbreviated with capital letters, E. S. And we're going to 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 in 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, thes 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 eat 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 letter peak. 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 toe form a complex with the substrate are predominantly mediated by non co Vaillant forces such as hydrogen bonds and Ionic bonds, for example. But that's not to say that CO Vaillant Bonds never form in the enzyme substrate complex, while CA Tallis this is occurring because they actually can occur. And we'll talk about that mawr 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 co violent forces. And so these weak non co violent forces that formed between the enzyme and the substrate in the enzyme substrate complex actually provide the driving force for enzyme ca Tallis ISS. And we'll be able to talk about this even Mawr in our next lesson video. So I'm excited to see you guys in the next video. So you guys there?

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 labeled 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 reactant. And so this arrow pointing to the very beginning of our curve is going to correspond with the reactions and the reactant oven enzyme Catalyzed reactions are known as substrates, which is options. See here. So we go ahead and label this era 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 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 it's 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 toe local maximum energy points because they're showing up at the top of a hill. And so because they're showing up at local maximum energy points, we know that these air both transition states so we can put the double dagger symbol here to show that these air both transition states now notice that the provided terms over here have two 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. So all we need to do Thio distinguish the non rate limiting transition state from the rate limiting transition state is to compare their energy of activations. And so if we look at this first transition state here, the energy of activation is gonna be the difference in energy from the substrate to the transition state. And so it will 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 gonna 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, uh, in comparison to the second one, this larger one has a larger energy of activation. So it's gonna be slower, and it's gonna be the rate limiting transition state. So we can go ahead and label uh, this one with Option E. And then, of course, uh, that we can cross that off and the remaining one over here is gonna be option d We cross that off. So that concludes this example problem. And I'll see you guys in our next video

So in our last lesson video, we said that the interactions between the enzyme in the substrate in the enzyme substrate complex predominantly consist of non co violent forces. And when these non Covalin forces formed between the enzyme in the substrate, they release what's known as binding energy and binding energy can be abbreviated with the symbol Delta G B. And the quantity of binding energy is defined as the energy difference between the uncapped ill ized and the catalyzed. Transition states. And again, binding energy is derived from the release of free energy when non covalin interactions form in the enzyme substrate complex. Now, later, in our course, we're gonna talk about the exact factors that enzymes influence toe lower the energy of activation. But in this video, what I want you guys to really know is that the enzymes lower the energy of activation by utilizing the released binding energy in order to stabilize the transition state in the active site. And so, essentially the main take away is that the way that enzymes lower the energy of activation is by stabilizing the transition state. And really, that's the major take away 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 in the substrate are able to interact with each other to form the enzyme substrate complex. And the enzyme is able to interact with 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 uncapped allies reaction is being shown as a dotted line so you can see that the transition state for the UN catalyzed reaction is really, really high. And unlike our previous reaction, energy diagrams noticed 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, and 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. Ah, 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 um, or realistic depiction of an enzyme catalyzed reactions. But moving forward, which will probably see, is that the enzyme substrate reactions are gonna be shown without showing the enzyme substrate complex. But here, which 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 uncapped allies and the catalyzed transition states. So again, the uncapped allies transition state is going to be the transition state that corresponds with the local maximum peak energy point for the UN catalyzed 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, which will 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, uh, speed up chemical reactions is by utilizing binding energy to stabilize the transition state. And again, that's the major take away of this video. So we'll be able to utilize some of these concepts in our next video. So I'll see you guys there