Enzymes


hi it’s mr. Andersen and welcome to biology essentials video 48 this podcast is on enzymes enzymes remember are chemicals that aren’t consumed in a reaction but can speed up a reaction one of the major ones we’ll talk about this year in AP bio is called catalase catalase is an enzyme it’s found in almost all living cells especially eukaryotic cells but what it does is it breaks down hydrogen peroxide hydrogen peroxide you probably knew growing up you put it on a cut maybe and it would bubble or you could use it to bleach your hair but that’s pretty dilute hydrogen peroxide actually concentrated hydrogen peroxide this is somebody who’s touched 30 percent hydrogen peroxide it damages and kills cells and so hydrogen peroxide is just produce naturally in chemical reactions but your cell has to get rid of it before it builds up an appreciable amount and it uses catalase to do that and so for you to look at the equation so we’ve got hydrogen peroxide or h2o 2 is going to break down into two things one is water and the other one is o2 oxygen and so this is not a balanced reaction so if I put a 2 there 2 and I put a 2 here so hydrogen’s I got 4 4 oxygens I get so perfect so this is a balanced equation so you’ve got two hydrogen peroxide breaking down into two water molecules and one oxygen molecule but it does that using an enzyme and so in other words hydrogen peroxide let me get my arrow to fit in here is going to feed into catalase and it’s going to break that down into these two products water and oxygen and it does that at an incredible rate I was reading that 40 million hydrogen peroxides will go into a catalase and be broken down into water and oxygen 40 million every second and so it’s incredibly fast at breaking down that hydrogen peroxide into something that can that it can use and so how does it do that well that’s what I’m going to talk about and so basically an enzyme let me try and draw an enzyme so if an enzyme looks like this it’s a giant protein so if we say it looks like that it’s going to have an area inside it called the active and so the active site I could do this good so the active site is basically going to be a part of the enzyme where there’s a hole in it so this is this giant protein it’s got an active site and the substrate is going to fit into it and so going back to how two enzymes work well the active site is going to be an area within the enzyme so this would be the enzyme here and basically the substrate fits into it and so what was the example we were just talking about the enzyme was catalase what was the substrate substrate is h2 o2 or hydrogen peroxide so that’s how enzymes work it basically tugs on the substrate and breaks it down it’s very important in chemical reactions and sometimes we want to turn on enzymes and sometimes we want to turn off enzymes and so in every step of photosynthesis in every step of the cellular respiration and glycolysis citric acid cycle all of those chemical reactions remember have to have an enzyme that’s associated with them that can speed up that reactions and so it’s really important that we sometimes activate or turn on those enzymes it’s also just as important that sometimes we turn them all turn them off and so there are two types of inhibition inhibition can either be competitive that’s where a chemical is blocking the active site or allosteric when we’re actually changing the shape or giving it another shape chemical reactions another important thing that we want to measure with them is the rate of a chemical reaction we can do that by either measuring the reactants or the products so let me stop talking about what I’m going to talk about and actually talk about it and so here is our enzyme so our enzyme that we talked about was called catalase so catalase is going to be a protein it has a specific shape and so if we go down here to the enzyme this would be the enzyme right here it’s going to have an active site an active site is the area where the substrate can fit in and so the substrate is going to be this green thing in this in this picture it’ll fit right in here and it fits almost like a key fits a lock and so it’s going to be a perfect fit between the two every chemical reaction is going to have a different enzyme that breaks that and so the important part is right here so now once we have the enzyme inside the active site is going to be a chemical tug in other words it’s going to pull on that chemical it’s going to lower its activation energy and so that can actually break apart into its products and so if this is our h2o 2 right here there’s going to be a tug on those chemicals sometimes it’ll actually change the pH sometimes it’ll put a mechanical tug on it but basically what it’s going to do is it’s going to make it easier for those chemicals to spontaneously break apart now hydrogen peroxide by itself h2o 2 if you leave it in a bottle for millions and millions of years if you come back it’s spontaneously going to break down into water and oxygen but that’s going to take years and years and years to do that and with an enzyme it can happen in seconds like I said 40 million hydrogen peroxides can feed through this create all of this water and can do that really really quickly and so enzymes are ready to go and so we want to control which enzymes are firing at which time and which ones are being released and so there’s basically a turn on and then there’s a turn off and so how do we turn enzymes on well there’s two ways that we could do that number one we could just not produce them until they’re needed and so lots of times we won’t produce a protein delts required and so we do what’s called gene regulation where we don’t even code those proteins until we’re ready to use them but also we can activate them and so activation is adding something to an enzyme to actually make it work and so you don’t have to remember the names of these but this is sus innate dehydrogenase and it’s a cool enzyme that’s used both in the citric acid cycle and the electron transport chain so this is going to be on it’s going to be embedded in that inner mitochondrial membrane and so it’s going to it’s going to run two specific reactions so it’s going to convert certain reactants into products but if you just build sus innate dehydrogenase by itself it doesn’t do anything it’s not going to work it has to be activated and so there are two types of activators those that are called cofactors and those that are called coenzymes and so if you’re to look in here there’s going to be things that have to be added to that enzyme before it can actually function and so the two types are cofactors coenzymes that came up with some that you might know cofactors are basically going to be small chemicals that are inorganic what that means is they’re not made up of carbon and so heam is an example of a cofactor heme is also what’s found in blood it has an iron atom in the middle and so that’s why we call it hemoglobin and so what it does is it’s it’s it’s creating that hemoglobin protein activating it and so cofactors are going to be in organic and so in other words they are not containing carbon and then we’re going to have Co enzymes and those are going to be organic and so they’re helping that enzyme to work example of a coenzyme would be thiamine and so thiamine another name for that is vitamin b1 and so vitamins are required organics that we need inside our diet and they help in enzymes function and if you don’t get enough vitamin b1 in your body then you die as a result of the neurological issue and same thing with with cofactors so these are required for life but basically what happens is once we have the cofactor cofactors and coenzymes now we have an enzyme that can actually function and now it can do what it’s meant to do but if we remove those cofactors if we remove those in organics and those organics then it’ll actually come to a stop or it won’t function anymore um so that’s activation that’s how we turn enzymes on but sometimes we want to turn them off and so let me kind of get you situated we’ve got our enzyme here we’ve got our substrate that’s going to fit here so if you think about it as an engineer for a second how could we stop that substrate again forty million of them coming through the active site in catalase how do we slow it down well there are two types of inhibition first one is called competitive inhibition competitive inhibition is when you use an inhibitor which is another chemical and you just get that but to bond into the active site so if you have that bonding in the active site then that substrate can’t fit in and so we’re going to stop the reaction so if we make a inhibitor that bonds to the active site we call that competitive inhibition because it’s competing for the space with the substrate now we can also do that non-competitive inhibition and we usually call that allosteric allosteric reaction works same way so here we are we’ve got our enzyme here’s our substrate it’s trying to fit into the active site we also have what’s called an allosteric site which is going to be another site on the enzyme itself and so one type of allosteric or changing the shape inhibition that we can do is we can have an inhibitor now that’s just going to bond to that allosteric site when it bonds to the allosteric site it’s covering up the active site and so now there’s going to be no way that that substrate can fit in but since it’s not actually bonding to the active site we call that allosteric allosteric means different shape or different shape of the enzyme so that’s a type of non-competitive inhibition or we can do it this way so this would be another type of knot of allosteric inhibition we can have a inhibitor bond to an allosteric site but if you look at the active site in this picture here’s the active site once this inhibitor bonds with the allosteric site it now changes the shape of the active site once you’ve changed the shape of the active site remember the substrate only fits if it’s like a lock and a key and now it’s not going to fit anymore so this is another type of allosteric inhibition and so we use feedback loops and we use inhibitors and cofactors and coenzymes to regulate what enzymes are going off at what time now when we do the enzyme lab we are using catalase and so when we do it in class we’re using catalase it’s an enzyme we use an enzyme that’s that’s found in yeast we then fill up a beaker with hydrogen peroxide we put our little disks of filter paper or Chad’s at the bottom we dip them in varying concentrations of the enzyme and then we see how long it takes for them to float up and so what we’re varying or the independent variable is going to be the independent variable is going to be the amount of the enzyme and the dependent variable is going to be how long it takes for them to float or the number of floats per second and so you could imagine let me get a better color if I increase the concentration of the enzyme we’re going to increase the rate of the reaction but eventually you can see how it starts to level off here eventually if you have enough of those let me change to a different color eventually it’s going to level off and so when we’re measuring reaction rate we could measure two things we could measure the products that are created or we could measure the amount of reactants that are being consumed in the enzyme lab we are measuring the amount of oxygen so we’re measuring the amount of products that are created but there are other things we can measure in this not only in the concentration of the enzyme we can measure the temperature we can measure the pH we can measure a lot of different things and remember organisms if we were to measure temperature for example the reaction rate is going to increase and eventually the enzyme is going to denature and so there’s going to be an optimum set point and since you have internal temperature of 37 degrees Celsius most of the enzymes inside your body are primed to work at that specific rate and so that’s enzymes and they are used to maintain that internal balance and I hope that’s helpful

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