one of the more important factors that may also affect the enzyme activity is temperature so let's do a quick one on how temperature can affect enzyme activity we prepare a few experiments as follows and in my following experiments here I've prepared five experiments as you can see here and the five experiments here they will all have the same concentration of enzymes which I've represented in the Pacman and also the same concentration of substrates which I have represented in the orange triangles okay so in this case here the only difference is for each of the experiment the temperature that the experiment is being conducted will be different 0 15 30 45 and 60. so when you conduct the experiments what we want to always see is the initial weight of reaction why the initial weight of reaction for each of them because it's the famous comparison of them all it's the famous of them all now so in the first for the experiment number one it this is by the way this results are theoretical which means to say these are not results you have to memorize this is just the way I teach it to my students to make it easier for them to understand so you see for experiment number one nothing happened none of the there were no initial weight of reaction because no enzyme substrate complex were formed at all so in this case over here the reason why it couldn't form was because the enzymes and substrates were probably moving too slowly for them to even meet each other for an effective collision at 15 degrees Celsius after one second perhaps theoretically two enzymes met with the substrate because the enzyme and substrate have a higher kinetic energy so they have a higher chance of forming a s complexes so the initial weight of reaction probably will be two products per second so at 30 degree celsius probably what might have happened is in experiment 3 there were four es complexes formed so as temperature increased the kinetic energy of the enzymes and substrates also increase even more so there's an even higher chance of forming the es complex at the same period of time one second so so far so good so as you increase the temperature the initial weight of reaction increases so when we plot the graph of initial weight of reaction against temperature we can see that as temperature increases the initial weight of reaction goes up all good now for experiment number four what do you think is going to happen to the initial weight of reaction so if you look at my graph you might assume well based on the line it looks like it should be going up even more but here's where something weird happens so in this case when you conducted the experiment there were no es complex formation at all after one second why can't the enzymes and substrates form the es complex so here's where we have to talk a little bit about the structure of proteins if you remember enzymes are just globular proteins and they are also having a 3D structure maintained by four types of bond in chapter two we've studied this hydrogen bonds ionic bonds disulfide Bridges and also hydrophobic interactions now for example if you look at my active site over here the active site is actually being maintained by some hydrogen bonds in the r groups so you don't need to memorize that I mean it's good to know but I just wanted to see the hydrogen bonds are maintaining the shape of the active site but if the temperature is too high the hydrogen bonds will break and when the hydrogen bonds break the mouth will start to become wider the active side shape will change because remember the hydrogen bonds were supposed to be there to maintain the shape of the active site but with no more hydrogen bonds to maintain it the entire 3D structure will change and when the enzymes 3D structure actually changes look at the substrate can it actually bind with the enzyme now the shape of the substrate is less complementary to the enzyme there is a lower chance for an es complex formation to happen when the 3D structure of the enzyme changed due to a higher temperature we will say that the enzyme is denatured so in this case I have to redraw my enzymes and I'll have to show you that the shape of the 3D structure is altered and when the shape of the 3D structure is altered perhaps what may happen is well it may be able to form the es complex but it will not be able to form four es complexes maybe in this case theoretically it might just form one es complex due to the difficulty of the substrate to bind to the enzymes so at 45 degrees Celsius the initial weight of reaction is one product per second as well based on my graph and for experiment number five at 60 degrees Celsius what will happen over here is the enzymes are fully denatured and because the enzymes are fully denatured because it has actually broken up most of the hydrogen bonds there is no more there are no reactions taking place at all so at at about slightly above 45 degrees Celsius to about 48 degrees Celsius okay let's assume it's 48 degrees Celsius the initial weight of reaction is zero now what I want you to see here is the graph for the initial weight of reaction against temperature is not technically symmetrical also that means at based on my graph here 30 degrees Celsius is the optimum temperature of the best temperature for the enzymes to function now what is very important to know is the graph is not supposed to be symmetrical when you're plotting a graph of initial weight of reaction against temperature what I mean by that is as temperature increases there will be more kinetic energy between the enzyme and substrates so more is complex formation so there will be a higher initial rate of reaction and at the highest point we will refer to that as the optimum temperature beyond the optimum temperature the initial weight of reaction will steeply decrease the graph is not symmetrical Please be aware of this all right so and as the temperature further increases beyond the optimum temperature we will see that the enzyme shape the 3D structure of the enzyme becomes even worse and becomes even less complementary to these substrates so at one point yes the enzyme shape has been altered slightly but it can form some es complex okay for that particular enzyme yes it's even more altered but it can still form ES complex yet the chances are much lower but for that enzyme over there which I'm circling the 3D structure of the enzyme is so warped it is so denatured that it can no longer form any es complex with the substrates at all therefore the initial weight of reaction is zero that is why we have to be very careful when our body temperature goes above 37 degrees Celsius you see our Optimum body temperature is always 37 degrees Celsius okay give or take about 0.1 to 0.2 degrees Celsius but the thing that we have to understand here is when our body temperature is too high that means we have an extremely high fever and it can be very dangerous for us because it may cause our enzymes in the body to denature so the weight of chemical reactions in our body will significantly drop that is why when a person goes to the hospital and they have a high fever usually uh let's say like in Malaysia if a person comes to the hospital with a disease known as Dengue and they also have a headache and they also have a high fever that means they have three problems going on at the same time the doctor will always usually prioritize ties the high fever first we have to bring the fever down to an Optimum temperature before they start dealing with anything else so it is very important to know that even beyond the optimum temperature reactions can still happen by the way as I'm plotting that in the graph but the reaction will be much lower compared to the reaction at the optimum temperature so this is what we have to know about the effect of temperature over enzyme activity