foreign okay so before I begin this video I'm gonna have to preface this by saying that my voice I may lose my voice or My Voice May Crack it's deeper than usual uh the reason is because I'm down with a little bit of a sore throat uh I don't think it's covet I did a test a self-test earlier and it's fine I don't have a fever but um I'll be coughing a little bit and I'll be sniffling throughout the video so I hope it does not make you uncomfortable and I hope the video will go by quite smoothly and I would also like to thank you guys for your kindness and support uh to my previous videos I think it's amazing and it just gives me the drive and the motivation to keep going all right so without further Ado we want to explain how enzymes work in this particular video and in the previous video I did say that enzymes are able to bind to the substrate and they are able to lower something known as the activation energy in this video we're gonna see how the enzymes actually lower the activation energy uh when it's uh in in an attempt to try to make the reaction easier to happen so this is my own example you don't have to memorize this example all right but in my example over here I'm drawing out a disaccharide and the disaccharide molecule is linked together by two monosaccharides represented by the two oval shaped structures and the chemical bond known as the glycosidic bond in the middle now for example if I want to break this glycosidic Bond by hydrolysis I will need to add water now just to revise back like the previous video if I have water at 30 degrees Celsius hit the glycosidic bond will it be able to break the bond No you see your able you you have water but the water is not able to collide with the glycosidic bond effectively because the water doesn't have much of a kinetic energy so the glycosidic bond will not be broken even though water was present now say I were to actually heat the water up to 100 degree celsius and the kinetic energy of the water is so high it's able to hit the glycosidic bond at such a high energy level and an effective Collision takes place and what happens to the glycosidic one the glycosidic bond has been broken so this is when hydrolysis is effective using water so if we were to just basically draw out an energy level graph remember because hydrolysis is an exothermic reaction where they substrate or the reactant will have a higher energy level the products will have a lower energy level you don't have to memorize this for biology that's more of a chemistry level knowledge but it's good to understand that at least okay so the red lines that I'm drawing or that represent their energy levels but to convert the substrate to a product you had to heat up the water to for example a hundred degree celsius so that an effective Collision would have taken place right and that extra heat you have to give is known as the activation energy I've told you all before in the previous video that activation energy is just basically the energy required for the chemical reaction to take place or an energy required to convert a substrate to a product foreign oh God sorry okay um now with the help of an enzyme however um I'm throwing up the two-dimensional version now enzymes are actually globular proteins they're supposed to be three-dimensional and I always love to represent my enzyme as a Pac-Man all right this is a reverse Pac-Man if you know what Pac-Man is a good if you don't know what Pacman is I think I'm officially old there were moments where I I will be teaching my students and I'll say oh this looks like Pac-Man and they'll go what is Pac-Man or who is Pac-Man and I just think to myself oh God bury me just kill me now all right I'll put me in the museum somewhere anyway so the enzymes actually have uh this weird little shape where it folds inwards known as the active site the active site is just basically the part of the enzyme that is able to bind to a substrate in this case the substrate being the disaccharide at the top left now it is very important if we zoom into the active side remember enzymes are actually just proteins and proteins are just basically made up of amino acids each of those green circles represent an amino acid and I'm also drawing out there are groups all right now what is very important is the enzyme must be able to bind to the substrate and for the enzyme to be able to bind to the substrate the active side of the enzyme has to be complementary to the substrate a common mistake students love to make in the exam is they love to say the enzymes active site has the same shape to the substrate it's not the same shape the shape is complementary if you say the shape of the enzyme and substrates are the same it's wrong the shape is matching or complementary that's a very important keyword to understand now when the active side of the enzyme is able to fit with the substrate at the glycosidic bond the arm groups where I'm highlighting over here will not break the glycosidic bond it does not break the glycosidic bond but for the lack of a better word the r groups disturb the glycosidic part it kind of just annoys the cloud I I don't like using that it annoys the glycosidic bond it interacts with the glycosidic bond to make it weaker and when it makes the glycosidic bond weaker water at 37 degrees Celsius will be able to break the glycosidic bond you don't have to heat the water up to 100 degrees Celsius anymore because the odd groups of the enzymes active site were able to interact with the bond and weaken it therefore in this situation over here with the help of an enzyme do you actually need to heat the water up to 100 degrees Celsius no for the human body the water can be at 37 degrees Celsius which is coincidentally our core body temperature so the water is able to break the glycosity bond at 37 degrees Celsius so what happens to the activation energy the activation energy in this case has been reduced by the enzymes that's what enzymes actually do fundamentally enzymes just make it easier for the reaction to happen by reducing the activation energy and how does it reduce the activation energy it reduces the activation energy by its active site binding to the substrate and weakening the bonds within the substrate that's basically it now just to summarize this back again I'm just drawing out an amylose molecule or starch at the top you can see many alpha glucose linked together by glycosidic bonds and it's very important for an enzyme to be able to bind the substrate I'm drawing out the primary structure of a polypeptide over there just a sequence of amino acids and what actually happens is that sequence of amino acid Falls to become a secondary structure you can see the alpha Helix and the beta pleated sheets and they fold further to form a tertiary structure if you need a revision on this I'm going to put a link in the description box so you can go back and revise your primary secondary tertiary structure and when informs the tertiary structure you can kind of see that Pac-Man kind of appearance okay this is just again my way of teaching enzymes do enzymes all have Pac-Man shapes no of course not they don't have that kind of like a quarter eaten pizza slice shape with an open mouth I just love representing enzymes like that that's just my way of doing it but point of the matter here is the enzymes are just basically made up of polypeptide chains and in this case here the enzyme has a tertiary structure and I'm just highlighting that area that area is basically known as the active site where I'm gonna put the amino acids with the r groups are represented in green and it's the same are groups that I'm drawing on the right side just to show you how it looks like on a simplified version and it's just very important for the active side of the enzyme to be able to bind to the substrate they are able to bind to the substrate because the active side of the enzyme is not the same shape but complementary or matching to the substrate other groups in the enzymes active site are then able to form a temporary interaction with the substrate is temporary it's not permanent here the enzyme will eventually have to detach from the substrate because it if it permanently binds to the substrate that it's useless and it weakens the glycosidic bonds which makes it easier for hydrolysis to take place now when I teach this a few students will make the observation do enzymes only help with hydrolysis don't they do other things as well if you notice my previous video I did say that enzymes do not just do hydrolysis different types of enzymes will cap will catalyze different types of chemical reactions I just like talking about hydrolysis because it is one of the easier chemical reactions to represent now as we can see here what happens is once the hydrolysis takes place the enzyme's job is far from over what does the enzyme do the enzyme just moves on to the next glycosidic Bond so that same enzyme can be reused over and over and over again so that it can break multiple glycosidic bonds that is the definition of a catalyst isn't it because enzymes are just these things that makes the reaction Easier by reducing its activation energy they will not be used up and they can be reused over and over again that's basically it