Enzyme Mechanism of Action & Activation Energy Explained

[00:00:02]so before I get to talk about enzymes and hexagonic and endergonic reactions I need to talk about energy so let's go back in time here for one second so first let's try to Define what energy is energy can be Loosely defined as the ability to do work any organism or entity that can that allows something to do work is something that is providing energy now they're essentially two two states of energy the first one of them is said to be the kinetic state or motion energy kinetic means movement so this is the energy that it's created as movement is created the other part like a name of energy is either a state of energy is known as the potential energy and this is the energy that gets stored after some sort of movement is produced now to simplify that usually people use this following representation here you think about a bike at the bottom of the hill that bike if you want to go up the hill you need some sort of kinetic energy so let's bring that bike up the hill now and then if as the bike gets to the top of the hill this kinetic energy is transformed and is transformed into potential energy because energy is never necessarily created I mean the person that provided the energy for the bike like to go up the hill somehow harvested that energy um from a vegetable for an animal that he ate and that plant that that the person ate actually had some stored potential energy because it Harbors the energy from the Sun it's never created but anyway let's go back to to our bike example here now that you are on top of that Hill you have potential energy and then if you want to go down the hill you're just going to use this potential energy to create more kinetic energy as you get to the bottom of the hill so very simple example showing like issue states of energy all right instead of trying to illustrate chemical reactions here I wanted to show what enzymatic activity looks like I'm going to use an analogy here let's think about um a pile of bricks I'm going to draw real fast here and this pile of brick is found on its disassembled state it's just a pile it's not completely disorganized and then if you want to move this pile of bricks to a more organized State you're gonna have to have some sort of energy input and then with this energy input you can create something that is known as a brick wall right so this is going to be the equivalent of my chemical reaction here now here my pile of bricks see it's the reactant of this chemical reaction and as it moves to the brick wall state it becomes the product of that chemical reaction so the blue error here indicates the the direction of the chemical reaction so let's imagine now what is going to be happening in this chemical reaction here as the uh on this graph here on the x-axis you have the progress of the reaction and then on the y-axis you have the molecules potential energy I'm using like of course we're talking about brakes here but like imagine if this was actually your if that was you assembling a bunch of carbon molecules into a carbon chain it would be essentially the same thing when you're combining chemical elements you are increasing their potential energy in many cases so what is interesting though is that I in this case here you are actually going from a state that has a a very very low um potential energy in the beginning true state like because this is where the reactants are to a state where you have like lots of stored energy lots of potential energy and you can actually start labeling like things in this graph here and you can actually like see that like the in the beginning even though those molecules were disassembled or the pile of bricks was completely chaotic you still have some energy stored in these reactants I mean that's like the the brakes have some sort of energy that can provide the resistance that or the the energy that it's uh stored in the brick wall now the other thing that you see here is that the energy stored in the products is a lot higher but what that tells you though is that like if you want to go from a state like from lower um potential energy state of higher potential energy you need to provide energy and this energy that gets provided to the system is known as the activation energy so on this reaction here energy input is necessary for the chemical reaction to occur because of that this reaction is said to be endergonic endergonic reactions are those that require a like an energy input and then in which the products also have a higher energy than the reactants now let's imagine now the the opposite of this let's imagine now that we're going from the reactance state to the products and but in this case now you're starting with the brick wall and you're moving to the pile of bricks well you imagine that this is a lot easier to do and because you actually start with the reactants that have like a lot of potential energy and it's very easy to move to the product that has a lower potential energy so again you can label like things here so the reactants have their their energy stored in them and this energy stored is much higher than the energy stored in the products and one thing that is interesting about this um like fake chemical reaction here is that the activation energy necessary for the reaction to take place it's much lower than um in in in the previous graph so these reactions because because you're moving from um reactants that have higher energy to products that have lower energy this reaction is said to be to to demand to to release the energy so this energy gets released you need a little bit of activation energy but overall you actually release energy for this chemical reaction and then we call this an exergonic reaction those reactions are said to be spontaneous because over time any brick wall comes down to a pile of bricks if you leave it long enough um this brick wall eventually just by chance will end up like becoming um a pile of bricks molecules that are really long and really well elaborated arranged like uh bricks in the brick wall eventually will collapse at some point now ah so you say that this is a spontaneous reaction that inevitably occur but that doesn't mean that it's an instantaneous reaction so uh and what prevents these reactions from being instantaneous is that is this demand for an activation energy so but as soon as this activation energy is provided the reaction will take place now following with my example here let's like try to understand a little bit more about this activation energy there are certain molecules that can reduce this activation energy so this molecule that can be added to the to the reaction is said to be a catalyst and its main property is to reduce the activation energy or make it easier for the reactions to take place a good example of catalysts are enzymes enzymes can facilitate chemical reactions by lowering the activation energy and making them easier to occur so again I'll go back to my example of the brick wall so I'm going to move like from the brick wall to the pile of bricks and what creates the activation energy for this brick wall to go to the pile of bricks could be any Force so in this case here I'm using the example of wind now if I were to be a catalyst if I were to be an enzyme on this chemical reaction what I would do I would like start like uh pushing this wall and in a way that can assist the wind so in that case here I am an enzyme assisting the wind of course I mean I would have to be really really strong like to actually provide some sort of energy that would assist them in depending on like how thick of the the mortar is in this brick wall but essentially I could assist the chemical reaction reduce the activation energy now I'm using here the example for an exergonic reaction but I think it's important to remind you guys that um catalysts enzymes can occur both in hexagonic and endergonic reactions now when um enzymes are actually acting they're increasing the rate of the reaction but they are not increasing the amount of product that is being formed in the end if I am the enzyme here I'm not adding more bricks to the pi on the very end I'm just making sure that all the bricks were that were there to begin with end up in the pile of bricks but I do not create more bricks so let's use like a real example of that so let's think about this chemical reaction here in which we're combining carbon dioxide and water and transforming that into this molecule known as carbonic acid without an enzyme this reaction occurs at two at a pace of 200 molecules per hour without the enzyme but if you add this enzyme known as this Carbonic anhydrase you increase the pace here quite a bit so in the presence of Carbonic anhydrase the reaction will occur at a speed of 600 000 molecules per second but again you're not creating more products you're just increasing the rate if you don't have carbon dioxide in water to conduct this reaction you simply will not like form six hundred thousand molecules you need six hundred thousand molecules of carbon dioxide to farm 600 000 molecules of carbonic acid all right so but how does that occur well it's not magic here the the enzyme's ability to reduce the activation energy has to do with the structure of the enzyme so let's see like uh an example here and in order to talk about this um structure of enzymes I need to talk about this key and lock model so I imagine here I choose substrates two reactants that we interact with an enzyme the enzymes represented at the top here and this enzyme you can actually get these two substrates and combine them and one thing that is very interesting here is that if you look at the shape of the enzyme if you look at the shape of the enzyme right here it corresponds to the shape of or roughly corresponds to the shape of the substrates all right and one thing that is very interesting is that as these substrates plug themselves with the with the enzyme the enzyme goes through a little bit of like a conformational change they change the shape a little bit so these little uh uh Small Change in the structure of the enzyme is known as the induced fit and what they induced if it does it can actually add stress to the chemical bonds of the two substrates in a way you can combine then or break them apart so the structure of the enzyme through the Endocet induces fit mechanism can add strength to the chemical bonds and allow you to essentially transform these two substrates into a new product so it's a very simple mechanism it's not necessarily magic is just well it just has to do with the structure of that enzyme now this key unlock model of course like determines that there's a specificity and and one thing that is very nice about the key unlock model as well is that even though the enzyme can actually accommodate the shape of the substrates the enzyme on the very end remains an altered if you go like compare this picture here the enzyme in the beginning of the reaction look essentially the same at the end of the reaction so the enzyme does not necessarily take part on the reaction it assesses the reaction but it's not one of the reactants is not becoming a product now uh I think this will actually summarize quite well the function of enzymes and I hope that this is uh going to be helpful for you in understanding like