Enzymes and Catalysts

okay so in this presentation we're going to discuss enzymes so let's go ahead and get started well before we discuss exactly what enzymes are we need to understand a little bit about chemical reactions no chemical reactions will absorb and release energy the picture kind of shows the chemical reaction the very basics of nuclear fusion and in nuclear fusion energy is absorbed and energy is released in order for a chemical reaction to occur energy is added to start the chemical reaction and this this is called the activation energy the amount of energy needed to start a chemical reaction you know the analogy you'll often see is this person pushing a boulder up a hill the amount of energy it takes for the person to get the boulder to the top of the hill is the activation energy once the boulder reaches the top and the guy can give it one final push the boulder will fall on its own the chemical reaction would then proceed on its own once the activation energy has been added to get the reaction started you'll see more of this guy in a few moments so when chemical reactions proceed energy is released usually in the form of heat and light energy is released because chemical bonds are broken during a chemical reaction so a good example is this chemical formula right here ATP which you might know is adenosine triphosphate which is a energy molecule that our cells will break down for energy so ATP with the addition of water when you bring the two together and when enzymes are included we'll talk more about enzymes in just a few moments then energy is released when ATP is broken down into a DP the energy that comes out is in this case in the form of heat and this is the heat that is used to warm our body so our cells do this example right here so there's a couple chemical reaction a couple types of chemical reactions I want to discuss one is called exothermic chemical reactions when you break the word into prefix and suffix you know EXO means to release or to give off thermic implies heat so the word literally means to give off heat so the definition of an exothermic reaction it's a chemical reaction that will release more energy than it takes in or then it absorbs and so when the energy is given off it's usually in the form of heat or usually in the form of light and so a great example of an exothermic chemical reaction is cellular respiration the process that breaks glucose down to make cellular energy here's the formula for for for cellular respiration c6h12o6 on the left that's glucose with the addition of oxygen will yield carbon dioxide water in energy energy for from cellular respiration is in the form of ATP adenosine triphosphate but this is why it's an exothermic reaction energy is released in the products of the chemical reaction when we talk about the opposite we're talking about endothermic reactions no endo is a prefix that means to take in or to absorb thermic again implies Heat so when you look at the definition of endothermic it's a chemical reaction that takes in or absorbs more energy than it will release a great example of this is photosynthesis I'm sure you all know that photosynthesis takes in sunlight energy to break down to to create sugar excuse me to create sugar and glucose that the plant will use for food when you look at the general formula of photosynthesis you see that carbon dioxide and water and light sunlight energy are used to produce sugar and oxygen again this is a great example why photosynthesis is an endothermic reaction sunlight is taken in to help jumpstart this process so I'm going to talk about what catalysts are and this is going to lead us directly into enzymes so a catalyst is a substance that will lower or decrease the activation energy needed to start a chemical reaction you know what if you're this person pushing the boulder if somehow the hill could be flattened and not so steep you would not need to spend so much energy pushing that Boulder over the edge well that's kind of what a catalyst does a catalyst will lower the energy needed to start a chemical reaction when you look at this graph right here this graph will show exactly what I'm Shoni what I'm referring to so the red line shows the energy that is needed for a chemical reaction to occur notice how the red line will increase and eventually begin the decrease near the end of the graph well what this red hump is here this is the activation energy this is the energy that needs to be added in order for the reaction to occur but with a catalyst notice how the graph is different with a catalyst the activation energy is much less the hump to get the chemical reaction started is much smaller so that's what a catalyst does now what are catalysts well heat is a great example of a catalyst so why don't we just heat the body up to help start all of our chemical reactions whoo I hope you see danger in that idea you really can't warm up the human body just a couple degrees above normal lands us in bed and we're sick and we have a fever and we feel miserable that's just with a few degrees above normal so there's a reason why heat is not used by cells as a catalyst I want to explore that a little more depth why heat is not used by ourselves as a catalyst well here's a good example here's one amino acid here's a second amino acid here's a third and here's a big growing chain of amino acids you might know already that a big chain of amino acids makes up a bigger molecule called a protein proteins are super important in maintaining our body in our cells so pretend that amino acid 9 is attracted amino acid 20 what happens is the chain of amino acids will twist and fold and Bend towards whichever they're attracted to pretend amino acid 1 is attracted to amino acid 5 ok and finally pretend amino acid 13 is attracted to amino acid 1 proteins have a final shape that will allow them to perform their function and the shape of a protein is very precise if the shape of a protein is altered in any way the protein typically cannot perform its function now this is a given to the reason why heat is a bad catalyst for cells so why don't we use heat as a catalyst well the notes say that proteins which are again very important molecules it within our cells and within our bodies proteins will degrade and break down and denature when they are exposed to higher than normal temperatures so if heat were used as a catalyst this would happen the protein would break apart the protein would no longer be able to function because its shape has been changed and this would lead to eventually a stopping of chemical reactions within our bodies and eventually our death so now we're coming to enzymes enzymes are the catalysts that are used by cells enzymes are involved in almost every chemical reaction within the body the picture of potatoes is because potatoes are full of a polysaccharide called start starch is very common to potatoes so let's zoom out in and so here's a very simplistic diagram of starch a big chain of glucose molecules and so there's an enzyme by the name of amylase amylase is an enzyme that will kind of act like scissors and will digest and break down starch into the individual monosaccharides so the enzyme here are the animated scissors and the enzyme amylase which is the specific enzyme in this example will continue to break down the starch into smaller individual glucose molecules into smaller monosaccharides and so again because enzymes are a catalyst they lower the energy needed to start a chemical reaction they will also increase the speed or the rate in which the chemical reaction will occur this specific reaction is this important reaction right here with the breakdown of starch and other chemical reactions this process would be just way too slow to sustain life without the use of a catalyst if we talked about this specific reaction of the breakdown of starch this is not an exaggeration starch is literally broken down a million times faster with the presence of the enzyme called amylase let's look at the structure of enzymes first of all enzymes are proteins so again here's a big chain of amino acids and because enzymes are proteins the enzyme will twist and fold and bend into a final shape and that shape will ultimately help the enzyme perform its function so here's a very simplistic diagram of the final shape of an enzyme notice how those little grooves cut out on top that's going to be really important so the enzyme the shape of the enzyme will actually attract very specific molecules and the molecules that enzymes will attract are called the substrate notice how there's like a v-shape channel and kind of like a peg shaped channel at the top of the enzyme well here's a substrate that the enzyme is attracting and so that those V shape that v-shaped cutout location on the enzyme and that peg like cutout of the enzyme this is called the active site this is the location where the substrate will actually bind to and connect with the enzyme so the analogy you'll often see is that the active site and the substrate are kind of like a lock and a key when the two fit they connect and they bind with one another so in my example of course here we see the substrate has binded to the enzyme well now what the enzyme will actually weaken and break the bonds that are holding the substrate together and ultimately there you see the substrate has been digested and broken down so what if the substrate does not match the active site well here's another substrate notice how the shape of this substrate is very different than the grooves and notches that you see on the enzyme notice what happened nothing no reaction will occur enzymes are very specific they match to a specific substrate so if the substrate and the active site don't match no chemical reaction will occur so a good example again I brought this up a few moments ago is the digestion of starch by an enzyme called amylase so here's the enzyme called amylase again simplistically and here's starch because starch is going to bind with this enzyme that makes starch the sub notice how the active site has the grooves that perfectly match the starch substrate and so because they match and they bind with one another what's going to happen next is the enzyme animes kind of acts like my animated scissors from a few moments ago the enzyme amylase will break down and digest the starch into smaller individual units so if you're in my biology class you're learning the difference between a hydrolysis reaction and a dehydration synthesis reaction so I want to kind of go over the role that enzymes play in this so here is a drawing a chemical drawing of sucrose for simplicity I'm going to draw it like this right here and what you see is that sucrose is a substrate and it will match into an enzyme into the active site of an enzyme and with the addition of water the addition of water and the action of the enzyme will help to break sucrose into two smaller fragments one called glucose the one on the left is glucose and the one on the right is fructose so this is kind of the role that enzymes play in hydrolysis well let's look at the role that enzymes play in dehydration synthesis here's a molecule of glucose on the left for simplicity I'm just going to draw it as a hexagon shape and here's fructose on the right for simplicity I'm just going to draw it as a Pentagon so here is an enzyme that will have a proper active site for glucose and fructose glucose and fructose would be the substrates so here we see glucose and fructose fitting into the active site of the enzyme now the reason this is called a dehydration synthesis reaction is because water will be removed watch this water is removed and in the process of that happening the glucose and the fruit the is bonded together to make sucrose a larger molecule when we look at the structure of sucrose here we can see it's one large molecule held together by that oxygen bond in the middle so this is the role that enzymes can play in building molecules as well not just breaking them down so there you have it I hope you found this video to video to be helpful if you're in my biology class feel free to pause the video write these answers down on a separate sheet of paper and I'd be happy to check your answers either before or after class thanks for watching

Channel: Beverly Biology

Views: 164,173

Rating: 4.8711276 out of 5

Keywords: enzyme, protein, catalyst, organic chemistry, chemical reaction

Id: PNyvtcu5-EU

Length: 16min 7sec (967 seconds)

Published: Sat Jul 23 2016