in this video, we're going to begin our discussion on the primary factors that contribute to the activation energy. And so recall from our previous lesson videos that the activation energy or the energy of activation can be symbolized with either of these two symbols. And really, all it is is the energy barrier that exists between the substrates or the reactions and the transition state. And so this energy of activation must be overcome in order to initiate the reaction and to convert the substrates into the products. And so just briefly refresh our memories. Let's take a look at this little energy diagram over here on the right, and so notice that we have the reactant or the substrates that this position and then we have the transition state way up here, which is a transient entity that exists at a local maximum peak energy point of the reaction and so literally the activation energy is just the difference in energy between the two here. And so this activation energy is what controls the kinetics or the speed of a reaction. And so the greater the energy of activation barrier is, the longer it will take for the reaction to take place, so the slower it will take for the reaction to go. And so here we have a question, and it's asking us what factors actually contribute to the energy of activation barrier. Well, it turns out that there are four factors that primarily contribute to the energy of activation barrier. And so the first is entropy. The second is proper orientation of the substrates. The third is the distortion of the substrate. And then, of course, the fourth is going to be salvation. And so moving forward in our course, we're going to briefly describe each of these four factors in their own separate videos. And so, really, the major take away is that the binding energy that's released when an enzyme forms non co violent interactions with its substrate will actually influence each of these four factors in order to decrease the energy of activation. And again we'll be able to see that more clearly when we talk about each of these four factors independently and so in our next lesson video, we're going to start with the first factor, which is a reduction in entropy. So I'll see you guys in that next video

So in our last lesson video, we said that there are four factors that primarily contribute to the activation energy barrier. And in this video, we're going to focus on our first factor, which has to do with entropy and enzymes are able to reduce the entropy and the random motion of their substrates. And so here's the set up for how this works when there's no enzyme that's present molecules and solution required collisions in order for the reactions to take place. But the problem is, is that molecules and solution also have lots of random motion. And so this rand emotion leads to a high amount of local entropy in the system. Now, what we mean by random Motion is that these substrates are moving in random directions, and the chances that they're gonna be moving in a direction that allows for a collision to take place is much lower. And so the mawr random motion that there is the lower. The likelihood is that the substrates are actually going to collide and the lower the likelihood is of the reaction taking place, and that will ultimately increase the energy of activation and slow down the entire reaction now, guys. This is exactly where enzymes come into play because enzymes air able to decrease the local entropy of the substrates in the reaction system by restricting the random motion of the substrates and bringing them closer together. And this will ultimately lead to the increased likelihood of the substrates reacting, which will decrease the energy of activation and speed up the entire chemical reaction. So let's take a look at our example down below to get a better visual of how enzymes reduce entropy and so notice on the left. Over here in this blue box, we have a scenario where there's no enzyme that's present, and in this scenario, notice that our substrates are are moving and random direction. So we have random motion of the substrates in solution and noticed that substrate A is moving in a random direction toward the left and substrate. B is moving in a random direction towards the bottom right, and so remember that these substrates need to be moving towards each other for a collision to take place in order for the reaction to occur. And so when there's lots of random motion, the chances of the reaction occurring decreases And so what we're saying is that there's, ah higher randomness in this scenario, and this higher randomness leads to, ah, higher energy of activation and that will ultimately slow down the reaction. Now, over here on the right, we have a scenario where there is an enzyme present and the enzyme is this red structure that we see here and so we can see that the substrates in this scenario are restricted. And so the restricted motion of the substrates in the enzyme substrate complex will ultimately lower the randomness of the substrates which will lower the energy of activation and speed up the entire chemical reaction. Now, some of you guys might be thinking, Wait a second, Jason, Didn't you say way back in our previous lessons that processes should increase universal entropy? So how is it that enzymes can get away with reducing entropy? Well, that's a great thought. And so essentially, the process is very similar to the hydrophobic effect, and so you can see that the molecules and solution are interacting with the solvent. And so there's ah, hydration shell around these solvent molecules. And so notice that when the enzyme substrate complex forms the hydration shell is removed, and so the water molecules that are removed in the hydration shell are able. Thio increase the universal entropy, even though the enzyme is decreasing the entropy of the local substrates. And so that's a great thought. And, uh, that essentially wraps up our lesson on how enzymes are able to reduce entropy and random motion in order to decrease the energy of activation and speed up chemical reactions. And so, in our next lesson video, we'll talk about the second factor that contributes to the activation energy barrier. So I'll see you guys in that video.

So in this video, we're going to talk about our second primary factor that contributes to the activation energy barrier, and that is proper orientation of substrates. Now, in our last lesson video, we said that when enzymes air not present substrates in solution, require a collision in order to react. But not only do substrates in solution required collision in order to react, they also require collision in a proper orientation, and so that's very important to keep in mind. Now, properly oriented random collisions between substrates and solution can be a pretty rare event, and that can ultimately increase the energy of activation and slow down the entire chemical reaction. Now, this is exactly where enzymes come into play because enzymes can use their binding energy toe, properly, orient the functional groups of substrates and increase the chances for a reaction to take place. And that will ultimately decrease the energy of activation and speed up the entire chemical reaction. So let's take a look at our example down below just to get a visual on how enzymes properly orient their substrates. Now, over here on the left side of our image in this blue box, we have a scenario where there is no enzyme that's present. And so in this scenario, notice that there is an improper orientation of the random collision. And so notice that substrate A has its functional group pointing in a downwards direction and substrate B has its functional group pointing in a backwards direction. And so even though these two substrates they're random motion, allows them to collide with one another, they do not have the proper orientation of the collision. And so the functional groups, because they're not properly oriented, they will not react, So there will be no reaction. Now, over here on the right, we have a scenario where there is an enzyme that's present and again the enzyme is the red structure. And so you can see that with the enzyme, there is proper orientation of the substrates in the enzyme substrate complex. And so notice that the functional groups are now in proper position to be able to react with one another. And so the functional groups are going to actually react. And so now we can see how enzymes are able to properly orient their substrates in order to decrease the energy of activation and speed up chemical reactions. So in our next lesson video, we're going to talk about the third factor that contributes to the activation energy barrier. And so I'll see you guys in that video.

in this video, we're going to talk about the third primary factor that contributes to the activation energy barrier, and that is the distortion of a substrate. Now. Many reactions require the distortion of a substrate into an unstable high energy transition state, and these distortions lead to an increased energy of activation, which ultimately slows down the entire chemical reaction. And again, this is exactly where enzymes come into play, because through the induced fit model, enzymes are able toe form interactions with the transition state throughout the reaction and the released binding energy can be used to stabilize distortions in the transition state and decrease the energy of activation, allowing for the entire reaction to occur faster. Now down below. In our example, images weaken better visualize how enzymes can stabilize transition state distortions. And so, over here on the far left in this blue box, we have a scenario where there is no enzyme present and notice that our substrate here requires distortion in order for the reaction to take place. And in this reaction, the amino group over here is going to interact with the car boxer group. But as it is right now, they are so far apart away from each other that they cannot interact. And so the Onley way that they could get close enough to each other is if our substrate here becomes distorted and takes on a high energy, unstable transition state where it bends in such a way where the amino group can be in close proximity to the car boxing group. But again, this is going to lead to a high energy of activation, and that's going to slow down the entire chemical reaction. Now the remaining of these boxes over here with the yellow background are scenarios where an enzyme is present. And of course, the enzyme is the red structures that are being shown now. When the enzymes first introduced, we know that the enzyme substrate complex is going to form, and from our previous lessons on the induced fit model, we know that the active site of the enzyme is not going to be perfectly shaped for the substrate, and instead, the active site of the enzyme is better suited for the transition state because we want to stabilize the transition state, and so over here we can see that the enzyme induced fit model allows for the enzyme to change confirmations, and it also allows for the substrate to change confirmations into the transition state. And the enzyme induced fit model actually stabilizes the distorted nous and the distortions in the transition state. So you can see we have this really distorted transition state here where the amino group is close to the car Boxer group. But our bar is being bent in a way that it creates an unstable high energy molecule. But our enzyme through these non co violent bonds that form is able to stabilize this transition state and that lowers the energy of activation and allows for the reaction to proceed faster and so that allows for the products to be released at a faster rate. And so you can see that a new bond was able to form between the amino and car boxer group over here, and we were able to split our substrate bar and half here, uh, toe break it open, and we were also able to release water. And so you can see here how enzymes are indeed able to stabilize transition states distortions in order to decrease the energy of activation and allow the reaction to occur faster. And really, this is one of the major ways that enzymes influence. The energy of activation is by stabilizing the distortions of a substrate. And so, in our next lesson video, we'll talk about the fourth and final primary factor that contributes to the activation energy barrier. So I'll see you guys in that video.

in this video, we're going to talk about our fourth and final factor that contributes to the activation energy barrier, and that is salvation or solvent interactions. And of course, in biological systems, the solvent is water. And so the salvation or the hydration shells that surround substrates in aqueous solutions can actually interfere with substrate reactions. And, of course, this interference is going to increase the energy of activation, which will ultimately slow down the chemical reaction. And, of course, this is where enzymes come into play again, because enzymes are capable of removing the potentially interfering hydration shells and replacing the hydration shell interactions with enzyme substrate, interactions that decrease the energy of activation and speed up the chemical reaction and so down below, in our example, weaken better visualize how enzymes dissolve eight substrates and so on the left hand side of our image in the light blue box. We have a scenario where there is no enzyme present and notice that even though the substrates are properly oriented and they are randomly moving towards each other, that the hydration shells that surround the substrates are capable of acting as blockers and essentially interfere with the reaction And so the interference of the reaction is gonna lead to, ah, high energy of activation, which is going to slow down the chemical reaction. And so over here, on the right, in the image with the whole yellow background. This is a scenario where an enzyme is present. And of course, the enzyme is this red structure here, and we can see that the hydration shells are actually removed in the enzyme substrate complex, and now the hydration shells cannot interfere with the reaction. And so that leads to a lower energy of activation which will speed up the chemical reaction. And so what you'll notice is that even though the enzyme is lowering the entropy of the system with local entropy of the substrates, the universal entropy is still increasing because these water molecules that break free from the hydration shell are going thio increase the universal entropy. It's similar to the way that we saw it happen in the hydrophobic effect in our previous lesson videos. And so essentially, what we can see here is that enzymes are capable of decrease in the energy of activation simply by diesel vetting substrates and removing the hydration shells and so that concludes this lesson here, and we'll be able to get some practice utilizing these concepts in our next video, so I'll see you guys there.