Transcript for:
Understanding Chemical Reactions and Enzymes

all right we're gonna be moving on to chapter three and this is the first half of chapter three and it's gonna focus on chemical reactions and enzymes so the first thing we need to talk a little bit about is energy and this chapter is gonna be talking about energy a lot because in the second half we're gonna be talking about cellular respiration how we get energy to make ATP energy is the capacity to do work and we cannot have two types potential energy which is stored energy or the energy of position and kinetic energy which is the energy of motion and they can be converted sort of back and forth from one class to the other so potential energy if you think about like pulling a bow back and holding that the bowstring like that that's potential energy right this is position and then when you let it go with it twins forward then it's gonna be kinetic energy or the energy of motion so there's a couple of places where we have potential energy in our body and one of them and we'll be talking about this a lot is that there's potential energy across the plasma membrane and usually there's a concentration gradient and this concentration gradient just means that there is a different concentration on either side of the barrier with the plasma membrane so let's say we have a plasma membrane and on one side we have a whole lot of sodium and the other so we don't have very much sodium we'll talk a lot about this in chapter 4 but the sodium is gonna want to go from this really crowded place with lots of other sodium it's gonna want to go to the other side of the membrane where there's not as much sodium and so that is so if we opened a door in that or you know a channel and that plasma membrane your sodium would all rush through and that's kind of a potential energy we also have potential energy in our electron shells and so electrons move from the higher to lower energy shell so our higher energy shells are out here further away from the nucleus and they want to get closer to the nucleus so electrons in high energy shells that are further away have potential energy and then electrons falling from those high shells have kinetic energy and they're moving towards the nucleus and we can kind of see like the electron is negative right and our protons in the nucleus or positives that are going to kind of want to be close to there and here is a review of our plasma membrane energy right where we have here is our plasma membrane and here is our high concentration of sodium and they all have high potential energy because they're all you know shook together in this one little spot and they don't want to really be so close to all the other sodium so if this door opens they want to go through and so when that happens the sodium ions that move to the area of low concentration have kinetic energy so the stored energy here that energy of position is going to be the potential energy and then as they move that's going to kinetic energy I'm Kenneth chemical energy is another form of potential energy and this is a really important one we have a lot of this in our body we use a lot of this energy is stored in the molecules chemical bonds and it's released when the bonds are broken and it's a little bit of a simplified view but that's basically what it is it can be used for movement the synthesis of other molecules and establishing concentration gradients so we just said the concentration gradient was the difference between the concentration of a substance in two different areas like on either side of this plasma membrane and so this chemical energy is present in all chemical bonds but molecules that are pretty important that we use to like store energy as are going to be triglycerides remember triglycerides were a storage form of what which biological macromolecule a storage form of lipids glucose and has glucose stored glucose can be stored in the body as glycogen usually in the liver and the skeletal muscle and then ATP right ATP we said is that modified nucleotide that's an energy the energy currency of the cell and it has those really high energy phosphate bonds at the end that when they're broken they release a lot of energy so all of these are going to be important in our energy storage so now we have a lot of kinetic energy forms in our body - and I'm gonna go over these pretty quickly they're a little bit more self-explanatory I think although this first one here is pretty important so we do have electrical energy moving through our body all the time I mean it's basically electrical energy is the movement of charged particles so the movement of ions especially so the movement of ions across the plasma membrane of a neuron is a type of electrical energy and this electrical impulse is going to be sort of the the way that our nerves are going to be communicating to our brain so our brain is is really good at interpreting electrical energy but not really the other types as well mechanical energy is exhibited by objects in motion due to applied force like our muscles are contracting for walking sound energy you have molecules that are compressed it's caused by a vibrating object so we have sound waves that are gonna come in to the ear and they're gonna cause our eardrum to vibrate radiant energy which is the energy of electromagnetic wave so a good example that is visible light striking the retina all right now retinas gonna be able to interpret that and a lot of these different types of energy I have to do with our senses like so this is our sense of hearing our sense of vision and we kind of need to have special receptors to understand these to accept these types of energy and transfer them to the electrical energy that the brain uses and then he he is the energy of electromagnet measured as the temperature of an object so armed in Chapter one we talked a little bit about homeostasis and how we use our muscles to generate heat in order to maintain body temperature and we can see this is a little bit of information about the electromagnetic spectrum so we have some visible light that the retina can perceive here and then we've got this area UV light and x-rays and gamma-rays these are going to be sort of those high-energy raves and they can cause mutations in our DNA when radio waves are or lower energy out there we won't talk too much about the electromagnetic but so now I want to briefly mention this is brief the laws of thermodynamics so thermodynamics is the study of energy transformations right and we said that energy can be transformed from one state to another but it can neither be created or destroyed so it can only change in form that's the first law of thermodynamics so energy can neither be created nor destroyed it can only change in form and but the second law of thermodynamics is going to state that when energy is transformed right so it's when it's changed in form some of the energy has lost as heat and so that heat is going to usually we can't use the heat necessarily to do work but in our bodies it's pretty important because we want to say to come we want to stay at a certain temperature so but when this happens that energy that's lost is heat we can't use that to do work and so the usable energy is kind of decreased and so as chemical energy converts the mechanical energy heat is produced and our like ira mitochondria are gonna help like as they're working through all of the what we'll talk about in the second part of this and aerobic cellular respiration the mitochondria are actually going to be you know changing energy around and they're gonna produce heat and that's gonna actually heat up the mitochondria and that's gonna happen a lot of things like skeletal muscle and that's gonna help heat up the cell so metabolism is going to be the term we learned about this in their first chapter we said this is one of the things that all organisms have they have metabolism and metabolism is the term for all the biochemical reactions in living organisms so it's the sum total of all the reactions and these chemical reactions that we're talking about are gonna occur when chemical bonds in existing molecular structures are broken and then new bonds are formed and so usually we have the old bonds and then we have to break those old bonds to form the new bonds and this can be expressed as a chemical equation so we'll say we have the reactants which are the things that we start with and the products which are the things that we ended with so reactants are usually written on the left side of the equation this is what we start with so in this case we've got the reactants here a and B and then the products are going to be what's formed by the reaction they're going to be written on the right side of the equation and so in this example C is the product and the arrow indicates the arrow of direction so the reaction direction so in this case we have a and B are combined and they form C and that goes in one direction in a balanced equation the number of elements are equal on both sides of the reaction so you know we might have two hydrogen's and an oxygen combining to form h2o so we would have the same number of about ends and elements on each side we can classify chemical reactions based on three different criteria so we can look at the change in chemical structure we can look at the change in chemical energy and we can see if the reaction is reversible or not so we'll first start looking at chemical structure and we've got three different types we have decomposition reactions synthesis reactions and exchange reactions and we've talked a little bit about these already when we talked about our biological macromolecules and how we take those monomers and make them into polymers or break them or polymers down into monomers so hopefully this will be a little bit of a review so this first part is a decomposition reaction so whenever we talk about a decomposition reaction we're talking about a reaction that has starts with a bigger molecule and makes two smaller or not necessarily two but makes more smaller molecules so in this example we have a B so one big molecule and then it's gonna break down into a plus B so we're breaking it down and so all decomposition reactions in the body together are referred to as catabolism or catabolic reactions and so remember we said that cats like to break things down so remember catabolism is the breakdown reaction we talked about hydrolysis reactions and we said the hydrolysis reactions were important in breaking down polymers into monomers and so what in a hydrolysis reaction we're going to be adding water right to break down that bond right here so this is an example here where we have group glucose and fructose together into a disaccharide called sucrose so we're adding water and this hydrolysis reaction and we're going to be so we're taking that oxygen here and we're adding breaking that bond over here we're adding hydrogen on one side and we're adding hydroxide on the other side and so now we have two separate monosaccharides glucose and fructose and so this is a good example of a hydrolysis reaction that we talked about in Chapter two now the opposite of this is gonna be if we start with two smaller reactions here or two smaller structures and we combine them to form a larger structure so a plus B equals a B and so a good example of this is a dehydration synthesis reaction right you it makes it makes sense that a dehydration synthesis reaction is a type of synthesis reaction and so the example that your book uses is once again from chapter two or we said amino acids are going to be formed by a dehydration synthesis reaction they're going to be formed into a dipeptide here and we've got a peptide bond formed in here so a dehydration synthesis reaction where we are going to be if it would be the same as this we were gonna be taking a hydrogen off of one side and hydroxide off the other side and then joining them together at that oxygen it's another good example of a dehydration synthesis so we call it dehydration because we're removing water and then those are a little bit simpler to look at but then we also have another type called exchange reactions and this is probably the most common in the human body and this is where we have groups that are exchanged between two chemical structures and so it's got elements of both decomposition and synthesis reactions and so we have a b plus c equals a plus b c so in this case we're moving the b from that first structure to the second and an example of this would be a fast way to regenerate ATP and muscle tissue and when we get to chapter 10 we're going to revisit this reaction but so this reaction here we have a creatine phosphate right and it's got this little phosphate group on the end and then we have an ADP adenine die five eight right adenine die five eight nine is useful is ATP though so what we really want to do is get that ATP back right because remember ATP is that I energy molecule the energy currency of the cell so we're going to have an enzyme here that's going to help it's gonna take this phosphate group off the creatine phosphate and move it to the ADP and now we have a creatine and an ATP so we've moved that phosphate group over and that's going to be an exchange reaction so we'll come back and revisit this one again this particular reaction again in chapter 10 and so we have lots of different types of these this is probably the most common well we're just moving things around and so a different a specific type of an exchange reaction is called an oxidation reduction reaction or you can call it redox reaction right so that's oxidation and reduction reaction and so this is a specific type of exchange reaction where electrons are moved from one chemical structure to the other and then they may be moved alone or with the hydrogen ion so a lot of times you'll see that hydrogen ion move with them too and so these reactions always have to occur together right so we always have to have an oxidation and a reduction because we're moving the we're taking the electrons from somewhere and moving them to somewhere else they're not just kind of disappearing or and we're not just getting them from nowhere from thin air so the structure that loses an electron is called we say it's oxidized during oxidation the structure that gains an electron is reduced during reduction and you can remember this by the acronym leo says ger so Leo le Oh Leo's a lion so losing an electron is oxidation says gurgi ger gaining an electron is reduction so Leo says ger to remember which one is which so losing an electron is oxidation gaining an electron is reduction Leo says ger and so this is important because we're moving these electrons and in a very big example of this is the nicotinamide adenine dinucleotide or nad nad plus over here we're going to talk about this a lot in the next lecture when we talk about aerobic cellular respiration and so anything has on different forms it has an oxidized form and a reduced form and so what happens is that this oxidized form right here can then accept electrons from other from other energy rich molecules and then once they accept the electrons it becomes itself an energy rich off so that it becomes reduced and then that reduced form is energy rich so it's kind of holding on to that energy so as electrons are moved just like we kind of talked about that electrons have potential energy in the position of electrons is important as removing these electrons you can think of it's like we're moving energy and so nor at first we have glucose which is an energy rich molecule remember we said it has a lot of energy stored in its chemical bonds and so we're going to oxidize that right so le o Leo losing electrons is oxidation and so it's going to lose its electrons and it gives up to hydrogen ion atoms also right because we said sometimes those hydrogen's are moved with the electrons too and then nad here which is already been oxidized is going to accept these hydrogen ions except except a hydrogen ion and two electrons and so it becomes reduced and as it accepts the electrons and becomes reduced it accepts their energy and then we have this energy rich molecule and then we also have a hydrogen ion that's formed so that glucose has that extra that extra hydrogen ion up here so here nad is going to be the oxidized form and it is able to accept electrons but it's not energy rich whereas the reduced form NADH right here has accepted those energy rich electrons and it has now become reduced and is an energy rich molecule and we'll be talking a lot about nad and NADH in the next lecture so remember them we'll come back to them so we can also classify chemical reactions by the changes in chemical energy so there's two different classifications here we can call them exergonic or endergonic reactions so exergonic reactions have reactions with more energies within their chemical bonds than the products do and so that means the ones on the that we stir with had more potential energy and the ones that we entered with have less and so that means energy is released so most of these are gonna be like decomposition reactions and we can see right here we've got an exergonic reaction so we've got the reactants like glucose and oxygen they have a lot of energy stored in their bonds and then the products of cellular respiration or carbon dioxide in water they don't have as much energy stored in their bonds so that energy has been released it has an exergonic reaction whereas the opposite of that is going to be this endergonic reaction this endergonic reaction we have the reactants have less potential energy within their bonds and the products have more potential energy within their bonds so that energy had to come from somewhere so we have to supply that energy in order for this I'm usually in the form of ATP in order for this energy in order for this reaction to go and usually these are going to be synthesis reactions and so I want to briefly talk a little bit about ATP cycling remember we said that ATP is the energy currency of the cell and the cells are going to continuously form and break down ATP it doesn't last very long when energy is released in exergonic reactions we said it doesn't just it doesn't just go away when we release a energy um we usually usually use that energy to form ATP and ATP is gonna then be able to like hold on to that energy and we can it makes it into a form that's usable by most of the things in the cell and so fuel molecule kills from food are oxidized and the energy in their bonds is transferred to ADP and a free phosphate to form ATP and so that energy that's been released from endergonic reactions is used to synthesize ATP and that ATP then we can kind of like move around and that the cell can use it very well ATP is then oxidized to aid in the endergonic reactions right we said endergonic reactions need energy to go and usually a CP is what is going to be used to fuel that reaction so the energy released from the hydrolysis of ATP from taking the phosphate off the end of that ATP provides energy in order to cause those endergonic reactions to be able to go now our body is like ATP is a good storage molecule for energy and it's really important that we have ATP and this cell can use it really easily but only a few seconds worth of ATP is present at any time because we're constantly using it and constantly making it so we have to continuously form ATP to provide energy and so here this is our ATP we have our adenine a ribose sugar and we have our three phosphate groups here and this last one here is that high-energy bond when we split ATP which is an exergonic reaction energy is released and we can that energy can then be used to fuel other endergonic reactions and then now we have adp it has two phosphates on it plus an inorganic phosphate over here and when we have an exergonic reaction remember we said X or ionic reactions release energy so that energy that's released from exergonic reactions can be used to form ATP so we can take this AGP and this phosphate and bind them together and that itself is an endergonic reaction so we use the energy supplied from the exergonic reactions to form other endergonic reactions now the last class location classification of chemical reactions that we have is what deciding if the reaction is irreversible or reversible and so you can look at the arrows in our chemical equation to try to figure this out so an irreversible reaction is just going to go in one direction so we have our reactants and they become our product and then they can't go backward right so we have a net loss of reactants and a gain of products and so it's kind of like if you are baking a cake right so you are taking all the ingredients and you're mixing them together and then you're making the cake at the end you have less ingredients and more cake and you can't really go back you can't like say oh but I need more sugar I want to take the sugar back out of the cake you can't really take it back out that way so that's it's irreversible once you fakes it the ingredients are gone but you have the cake where as a reversible reaction is going to be sort of different it doesn't only go in one direction it can go in both directions and so it's usually indicated by these double arrows here and so we don't have any net change in the concentration of either reactants or products they're gonna be at equilibrium because we can have these to think of like Legos when you think of a reverse flow reaction where you can take all of your individual Legos and put them together and build like a Lego castle but once you're done with that you don't like if you need more Legos you can always break them back down and get the individual Legos back right so you can put them together and you break them apart you put them together and you break them apart and so you know if you want to build more stuff then you know just put them together and build more stuff if you need to use more individual Legos you can break it back down and so one important thing to look to know and think about reversible reactions is that these are going to always exist at equilibrium and so we usually have about the same amount of a plus B as we do a B and so think about like if you have an increase in reactants so if we have a lot more of these individual A's and B's we've got a whole pile of new Legos that you know we haven't built yet then it's gonna kind of cause you to be like oh I really want to build more stuff and you're gonna make more Lego models right and so an increase in reactants is gonna cause it's gonna drive their reaction drive the equation to the right as you add more reactants that's going to build you're gonna build more models but then a decrease in products is right here or a decrease in products will also try the equation to the right so if for some reason you don't have very many models that are built at all you might want to build more models like you have to you know just more of them so if you have more products or more reactants or less products you're gonna build more if you have less reactants or more products you're gonna break down more and so like if you have very few individual Lego blocks left but you have a whole bunch of models that are built maybe you don't have enough room for the models or something and so you're gonna break those back down again and so you're gonna kind of have a similar like pile of the a and B together a similarly sized pile of reactants and a similarly sized pile of products and they kind of need to stay in equilibrium this concept is going to come back we're going to talk a little bit about it again in 169 so just remember that these reversible reactions are going to remain in equilibrium so an increase in reactants or a decrease in products is going to drive the equation over to the right whereas a decrease in reactants or an increase in products is going to drive the equation over to the left there is a good table in your book that goes over all the different types of all the different classifications of these different reactions so you can look at that table and that you know use that to organize your thoughts so next I want to talk a little bit about reaction rates so reactions can either be fast or slow right so a reaction rate measures how quickly a chemical reaction takes quick takes place and in order to figure out how quickly it happens we need to figure out what the activation energy is the activation energy is gonna be the energy that's required to break those existing chemical bonds so we said before this whole reaction happens we have to break the bonds that are already there in order to make new bonds and so we always need to add a little bit of energy at the beginning to break those bonds and so this activation energy it's a big eighth a big you with a little a down there is a primary factor to determine the reaction rate so in order to start this reaction we have to add some energy and it sometimes takes time to do that we have to overcome there the activation energy and so this picture right here is going to show us this is like the activation energy here and then eventually so even if this is going to be an extra comic reaction where we're eventually going to release energy we need to add a little bit at the beginning this activation energy and so this is an initial hump we're like so we have to save up some energy it's gonna take a little bit of time before we can get enough energy in order to let this reaction proceed and so in order to overcome their reaction energy we need to like or overcome the activation energy we need to provide enough energy in order for this to happen and the faster we can provide the energy you know the faster the reaction will happen and in a lab what we can do is we can increase the temperature and by doing that that provides energy to break the bonds but significantly increasing the temperature in your body is not really that helpful because it's going to possibly denature those proteins remember kind of melt the proteins and it changes their shape and that is going to be not good for your body and right you don't really need to have a really high body temperature all the time and so instead of you know increasing the temperature in your body we use something called a protein catalyst or an enzyme is use instead and enzymes are going to be what we'll talk about for the rest of this lecture so enzymes are catalysts that accelerate normal physiologic activities so they don't cause things to happen that wouldn't already happen but if those reactions would have happened um but maybe it would take a long time for them to happen this enzyme makes them happen more quickly and what how it does this is by decreasing the activation energy of the reaction we call a reaction that's on catalyze a reaction that has no enzyme present and then the catalyzed reaction has an enzyme present and so this is going to increase the rate of the reaction and increase the rate of the products being formation so in this case here our example is an exergonic reaction right so we said we have sucrose we're going to break it down into glucose and fructose so this is that same example we used earlier and so here is the normal activation enzyme that's uncannily without the enzyme we would have to save up you know a lot of energy before we can actually have this reaction occur but what the enzyme does is the enzyme is gonna kind of group these it's gonna like bind to the two sucrose here and kind of give it a hug and it's going to change the shape of the this area here and it's going to make it so that it takes less energy to break those bonds and so it decreases the activation energy and so by decreasing the activation energy this can happen faster and I like to think of let's say you're saving up for something like you want to buy you know something from the store and it's $100 and you know let's say you're you're like a kid and you're trying to buy a bike that's $100 but you only get allowance you get like you know five dollars a week or something so it's gonna take a long time right it's gonna take twenty weeks to get your bike because you know it takes a long time to save up that money but what if the bike goes on sale right and if the bike goes on sale and it's you know oh it's fifty because this looks like it's about 50% let's say it's 50% off you know well then if it's only $50 instead of $100 then it's only gonna take ten weeks instead of twenty and so it's gonna happen faster right because you don't need to save up as much energy and so you can definitely save that up more quickly so by decreasing the activation energy the enzyme is going to increase the reaction rate so it makes the reaction happen faster right so what exactly is an enzyme an enzyme is a protein so remember we looked at biological macromolecules and we talked a little bit about proteins and protein structures and most of these enzymes are globular proteins and globular protein is a big sort of it's not a straight like thin protein is a big sort of gulabi protein so most of them range from about 60 amino acids to you know 2,500 amino acids so that they are pretty there can be very small ones and very big ones and they have a the shape is very important like I said before for proteins the shape is really important to how they function and so this has a unique three-dimensional shape sort of inside the protein called the act of site and this is where our substrate is gonna bind and so here this is the enzyme you know big and globby it has this opening this hole called the active site and it's the exact size and shape of the substrate and so the substrate will fit right in there and it kind of gives it a hug and this means that it the active site can only bind to this one substrate right because the shape is different so it only bonds to the one type of substrate and therefore each enzyme is only going to catalyze one specific reaction and so it's going to you know give this enzyme a hug decrease the activation energy and you know cause the reaction that happen more quickly so some of these enzymes are gonna be within cells so like DNA polymerase is within the cell right it helps form new DNA um some of them become embedded in the plasma membrane of a cell and so an example would be the brush border enzymes in the small intestine so lactase is in the walls in the small intestine and it helps digest lactose as we drink it from milk and some of them are secreted for the cell from the cell so a good example of an enzyme is pancreatic amylase it's released from the pancreas and it helps on participate in starch digestion so enzymes are how exactly do enzymes work so how do enzymes catalyze things and so enzymes remember we said they have this active site and this active site is very specific and it only binds a specific type of substrate so that substrate the one that fits is gonna go right there and it fits like a lock in the key it's gonna fit into this I'm active site and it forms what's called an enzyme substrate complex the enzyme then changes shape slightly and it's going to this is going to stress the chemical bonds and so it decreases the activation energy it makes it easier to break those those old bonds and it lets the new bonds be formed more quickly then the products are released and the enzyme is not harmed in the process so it can catalyze hundreds of reactions the only the one type of reaction but it can do it a hundred different times like many different times and so here we have lactase right here we said this is going to be embedded in the small intestinal wall the micro villi of the small intestine so it's going to like fit well with this lactose and so it's gonna give it a hug like this and it's gonna stress those original bonds and kind of help break those original bonds and then decreases that activation energy so that we can have the glucose and collect and galactose are gonna then be free and now as we can see lactase is still it's still healthy and it can then go back and catalyze another reaction so it is not destroyed in the process it's also can be used in synthesis reactions so here like in the liver when we're storing glucose as glycogen we have the enzyme glycogen synthase and it's going to bind it to separate glucose molecules and then remember that we had we have to take a hydrogen ion off one and hydroxide off the other in this dehydration synthesis reaction first like break those initial bonds before we make that new bond at the oxygen so it's gonna change the shape a little bit decrease the activation energy help those initial bonds be broken and then make it easier to form the bond between the glucose molecules and then glycogen is released and the enzyme is free to participate in another reaction so it is important that these enzymes are regulated that we regulate the enzymes and how they work and one of the things that we used to regulate the enzymes are activate them is a cofactor and cofactors and coenzymes cofactors are molecules or helper ions that are required to activate the enzyme ER to ensure that the reaction occurs so these are really important and we have lots of different enzymes that require lots of different cofactors or coenzymes so if we have these are not proteins usually but they can be either organic or inorganic in structure so an intergal cofactor is like a mineral like a zinc or something like that so these minerals are gonna attach to the enzyme to help it work and so each enzyme you know is going to need different types of these cofactors so an example is that a zinc iron is required for carbonic anhydrase to function and this is an important enzyme that we'll talk about in 169 so we need zinc in our diets in order for this enzyme to function and that enzyme is important for making you know important reactions occur now if our cofactor is organic so if it has a carbon hydrogen we call it a coenzyme instead and so these coenzymes a lot of them are vitamins so like B vitamins are really common and very important coenzymes sometimes they're modified nucleotides that can serve as coenzymes and so these coenzymes like nid and things like that are going to be really important in like they need to be present in order for that enzyme to work and so in order for all of those molecule in order for all the reactions to happen as quickly as they need so these are very important and we need each different enzyme is going to require different cofactors and coenzymes in order for the reactions to occur in order for them to be active so once the enzyme is active right and we have the enzyme that we have substrate we can we know that what does the enzyme do it increases the reaction rate so it makes the reaction happen faster but if we only had one enzyme and we had a whole bunch of reactions that needed to happen you know the reaction still wouldn't happen that fast and so sometimes we need more than one enzyme in order for these to happen so as we look at the rate of the chemical reaction if we just added one enzyme it's not going to increase the rate significantly but if we added you know ten enzymes or twenty enzymes it would increase the the rate a lot faster so the rate of the chemical reaction is going to be accelerated by a couple of things so we can make the chemical reaction faster by increasing the enzyme concentration so we need to add more enzymes and so if we add more enzymes that's going to make the reaction happen faster because we have more enzymes that are ready to you know catalyze that reaction so here we can see that the rate of the reaction is going to this next part sorry it makes sense that if we add more enzymes the rate of the reaction increases but now we can also increase the rate of the reaction by adding more substrate and the substrate is the stuff that the enzyme uses right remember that enzyme substrate complex so if we have say a hundred enzymes but we only had you know ten substrates adding more enzyme is not gonna help because we don't have enough you know substrate in order you know for all those some of the enzymes aren't busy already and so if we have you know a whole bunch of substrate and we have only a couple of enzymes then adding more enzyme is going to help if we have a lot of enzymes and only a little bit of substrate then adding more substrate is going to help so if we add more substrate it'll increase their rate of the reaction up to a point but like I said before if we have 100 enzymes and only ten substrates then the reaction rates gonna be slow so we can add more substrate so if we had 100 enzymes and 50 substrates then the reaction rate is faster if we have 100 enzymes and 80 substrates than their the reaction rate is faster if we have 100 enzymes and a hot 100 substrates then that's like as fast as it could go at this point though if we continue to increase our substrates so if we have you know 200 substrates and stand only 100 enzymes then it's not gonna release it's not going to increase the reaction rate anymore so if we have more substrate than enzyme so once the enzymes are saturated which means every enzyme is bound to a substrate if we increase the amount of substrate any further above this point it's not gonna increase the reaction rate at that point we would need to add more enzymes so I guess ideally the best thing would be if you had the same like you were right here this is the best your enzymes are saturated you have the same amount of Endre enzymes as you have substrate and that's kind of as fast as you can go so if we add more enzymes then we can N and n to add more substrates than we can increase the rate or the rate of the reaction so another thing that we can do is that temperature increase is going to be important in affecting their reaction rates and so as we said before in a lab we can increase your reaction rates by increasing temperature and so we can do this a little bit in the body right if you have a like a mild fever right your your enzymes will work a little bit better but remember that our enzymes are proteins and proteins are very very dependent on their shape the three-dimensional shape and this three-dimensional shape isn't dependent on temperature so if our if we have a moderate fever um the enzymes are actually a little bit more efficient and so at moderate fever then our enzymes our reactions will happen a little bit faster so but if we have really high increases in temperature it's gonna actually denature the proteins and denature the enzymes and so that's gonna lose their function they won't work anymore all the proteins are gonna kind of melt and it's gonna decrease the term decrease their reaction rate so for here most enzymes work pretty much best at normal body temperature around 30 37 degrees see a little bit higher helps a little bit so if we have a mild fever that's okay it makes our enzymes work a little bit more you know mild but once we get any higher than that you know you're like at 106 temperature that's not good okay you're going to be starting to denature and like melt those proteins so they don't work as well anymore pH is also a big effector and how on the reaction and how the enzymes work and so enzymes are gonna function best at their optimal pH and so normally right the pH of the blood as we talked about in chapter 2 is around 7.35 to 7.45 and so since most of our enzymes are gonna be found in the blood and their body tissues which are around 7.35 to 7.45 most of our human body enzymes work best between somewhere between a pH of 6 and 8 and if we change the pH a lot it's going to disrupt the electrostatic interactions between those you know the three-dimensional protein shape and it can cause it to denature again and so if the pH gets too acidic then it can denature the protein oh and if the pH gets too basic it can denature the protein so really we want to keep the pH of our blood the same like right there at 7.4 we don't want to change it too much now some enzymes though are special and they're I'm going to be modified to work in a special environment so like in our stomach we have stomach acid that's around a pH of 2 and so we do have some specialized enzymes that are that work best at a pH of 2 and so they're gonna work best in the stomach but then if they leave the stomach they won't work as well at other temperatures so each enzyme has its own optimum pH so now I do want end with controlling enzymes so we said that we need in order to activate those enzymes we need cofactors or coenzymes to be present and so that's one way we can control them we can you know activate them with those cofactors or coenzymes but we can also inhibit them and in hip inhibitors are going to basically turn them off so inhibitors are going to bind to an enzyme and prevent them from doing their job and so this is important because sometimes we want their reaction to happen fast sometimes but not all the time like once we have enough product we can kind of turn off that assembly line right we don't need to keep making more products usually the inhibitor binds to the enzyme for a little while and later it can release and that will let the enzyme work again so it's like when it's bound we turn the enzyme off and when it is not bound we can turn it back on again so now there are two types of inhibitors we'll talk about and the crack the I think Bozeman science I think that I linked as an ED puzzle goes through enzymes pretty well and it talks about these different types of inhibitors so inhibitors can either be competitive or non-competitive so it's repetitive Bend means it competes with the substrate and when by that I mean both of them bind at the same active site and so competitive inhibitors generally resemble the substrate which they would have to in order to fit into that active site because there's this lock and key so this inhibitor is going to be a similar shape to the substrate and it competes with the substrate to bind at that active site but when the inhibitor binds of the active site instead of you know having a reaction happen it kind of turns off the enzyme it's like a cap covers it up it makes it so no other substrate can get into there and so because this is competitive if we have a lot more inhibitor than the inhibitor is going to win out right and and the enzyme will be inhibited but if we have a lot more substrate then sometimes the substrate can beat the inhibitor and the substrate can get there and so if we have more substrate a competitive inhibitor is not going to be as useful so the other type is a non-competitive inhibitor a non-competitive inhibitor doesn't resemble the substrate and it doesn't bind to the active site instead it binds to a different site called an allosteric site another site and so what it does is it binds that allosteric site and a lot of times it causes a change in the shape of the active site and so that change in the shape of the active site and then means the substrate doesn't fit and so once again this is kind of like a switch when the inhibitor binds it turns off the enzyme it makes it so the substrate does not fit in this active site anymore because of this because they don't compete for a spot in the active site then it doesn't matter the substrate concentration doesn't matter this allosteric inhibitor here whenever it's present it binds to the allosteric site and it totally turns off the enzyme so it doesn't matter how much substrate is there if the enzyme is turned off so they are not influenced by the concentration of substrate so the last thing I want to talk about is how enzymes are arranged together and so usually when we have some sort of reaction especially if it's a complex reaction like aerobic cellular respiration which we'll talk about next time these enzymes we might need multiple enzymes so in order to convert the initial substrate to the final product like glycolysis uses like a chain of ten enzymes in a row and there's a couple of different ways that this can happen so a metabolic pathway is called is a series of enzymes and this series of enzymes is going to be the product of one enzyme becomes the substrate of the next so this is like the chemical breakdown of glucose is a metabolic pathway and so we have the initial substrate here is going to then bind to the first enzyme and turn into this you know marine one that's the product from enzyme one the products of enzyme one is then substrate for enzyme two which is going to turn into into this orange one which is the product of enzyme two which turns into the substrate for enzyme three and so on and that substrate from enzyme three is then going to turn into the or the product from enzyme three turns into the substrate for enzyme four and so on so this precedes kind of in an orderly manner and a lot of times they might be embedded in the plasma membrane so that you know they are close to each other and they kind of stay close together now we'll come back to that picture in a second the opposite of this is a multi-enzyme complex and this is where these enzymes are actually attached to each other and so they're kind of attached in one big glob and they work in a sequence of reactions and like pyruvate dehydrogenase is an example of that so there is some example some advantages for the multi-enzyme complex so if all of them are directly together in one big glob it's less likely the substance will diffuse away into a different pathway right because they're all together and they can go the substrate will go through very quickly and then this single complex can be regulated rather than individual enzymes so we only have to regulate you know that one complex instead of regulating you know each different enzyme on pathways those multi enzyme or the metabolic pathways instead of regulating each individual enzyme in this multi enzyme pathway so let look here we don't have to necessarily turn off each of these our multi enzyme pathway is pretty cool because it can actually be regulated by negative feedback so the first enzyme in the pathway here has an allosteric site and as we said they kind of go in a row so the substrate comes in and it turns into something else and it keeps going it keeps going and at the end and if I'm for releases the end product so this is the end product this is whatever we wanted to make and then this end product here is gonna go back and it's going to then be the allosteric inhibitor for enzyme one so once we have enough of the end product once the end product starts building up it'll actually some of it is gonna then be able to bind at the allosteric site for enzyme one and turn off enzyme one so once we have enough product we don't need to make more product the product can go back and it can bind to the first enzyme here and so when that happens the initial substrate will never be turned into the intermediate substrate so there won't be any green cells like there will be this green triangle there won't be this orange square there won't be this you know blue hexagon and so we don't actually have to turn off these other enzymes necessarily because if we turn off the first enzyme then there those intermediate substrates are not going to be made and so it kind of turns off that whole pathway so another way we can regulate enzymes is by phosphorylation or D phosphorylation and so phosphorylation is the addition of a phosphate group and this is performed by protein kinase a--'s and this turns off some enzymes and turns on others and there we'll talk a lot about protein kinases so adding and removing phosphate groups are pretty important for a lot of things dephosphorylation as the name implies is their removal a phosphate group and it's performed by phosphatases so kinase is phosphorylate things phosphatases d phosphorylate things this once again just like phosphorylation turns on some enzymes and turns off others so drugs can be really useful as enzyme inhibitors so we can look through and we can figure out how to increase or decrease a specific enzyme activity and this can sometimes like modify homeostasis and so for example penicillin actually targets a bacterial enzyme which slows the spread of infection so if bacteria inhibits the if the penicillin inhibits the bacterial enzyme it's gonna slow down the bacterial bacterias the reaction in the bacteria and that slows the spread of infection sildenafil or viagra inhibits phosphodiesterase type 5 right and phospho destroys type 5 is a specific type of enzyme and by inhibiting that enzyme it's gonna cause vasodilation of the blood vessels in the penis so we can use a lot of drugs or going to target enzymes and either make them more or less effective and so for example lactose intolerance right so we said a lot of times lactose intolerance happens because an individual does not have that lactase enzyme in those micro villi in the brush border so lactase is required to break that bond into lactose in lactose and form glucose and galactose a lot of older adults don't have that lactase anymore it doesn't persist and so you can treat that with taking like lactaid which has lactase enzymes and so if you you know take the lactase enzymes along with drinking you know milk or whatnot it's gonna help break down those break down that lactase so the last thing I want to mention and I don't have a picture of it here but I did put it in your it should be up I'll put it up for you in the book you have a nice table that talks about all the different types of enzymes and it gives examples of all the different types of enzymes so naming enzymes is pretty important anytime you something that has an ASE at the end ASE lactase it's usually an enzyme and if you look through your book has a table of all the different classes of enzymes and I'll see if I can uh well at some point you can look through I don't remember the number of the table and [Music] that enzyme is going to be really important in or then knowing that knowing the names of enzymes or the type of enzymes will be really important