in this part of module 4 we're going to be or you're going to be learning about ATP um co-actors co-enzymes enzymes um inhibition metabolic pathways kind of the foundation to then go full into cellular respiration in the next part so I've been talking about ATP about being the main energy carrier in cells ATP is a modified nucleotide it's stands for adenosine triphosphate it basically has the ribos sugar as in a nucleotide from RNA it has the adenine base and then it has three phosphate groups attached to the carbon 5 Prime over here now the most important part of the ATP molecule uh it's really these three phosphate groups because this is where the energy uh resides this calent bond between the phosphates are high energy bonds that are quite unstable so when we are talking about the hydrolysis of ATP that means breaking down ATP or removing the terminal phosphate groups from ATP when that phosphate is removed this is considered an exonic process because energy is released in that way when a fos phate group is lost then ATP becomes now ADP or adenosine D phosphate because now there's only two phosphate groups so that's why ATP it's basically very important because that energy that is stored there can be tapped by removing one of those phosphate groups however we also going to learn that cells need to build ATP okay when when cells are consuming glucose and that glucose need to be broken down into um into or not broken down but yeah broken down but the energy that I store there will be used to build ATP then the opposite process need to take place in which now we have to start with ADP and build ATP by adding that phosphate back there now that that's difficult to do because now we're trying to show a phosphate group group in there causing more strain to the molecule so the synthesis of ATP is endergonic while the hydrolysis of ATP is exergonic there are three ways that cells or three mechanisms uh that are found in cells to build ATP the simplest one is called substrate level phosphorilation in this type of process an enzyme such as a kise is going to transfer a phosphate group from a phosphate donor high energy phosphate donor such as phospho inal pyate and it's going to transfer it to ADP to create ATP even though it sounds very simple that's actually very hard to do because there are not many high energy phosphate donors just laying around in the cells waiting for them to be hydrolized so the most common way to do that is either by oxida phosphorilation in cellular respiration or by photo phosphorilation in photosynthesis both processes are very similar the only difference is where those electrons are coming from that's basically it uh both oxidated phosphorilation and photo phosphorilation use an electron transport chain that means that this process needs to be needs to take place in a membrane again if we're going to be talking about the uh oops the structure to okay um we're going to we already talked about the um membrane or the Etc in the past that membrane it depends which one we're talking about if we're talking about bacteria is the only membrane that they have that is the plasma membrane if we're talking about eukaryotes then in the case of cellular respiration that will be the inner mitochondrial membrane and in the case of photosynthesis that will be the thid membrane this is the process by which electrons are going to be transferred in that case a proton mod force is going to be produced that's the accumulation of H+ ions on one side of the membrane and then and then those ions are going to flow back to the other side of the membrane through an enzyme called ATP synthes that is going to provide this endergonic process of shoving a phosphate group back into ADP to form ATP all right in terms of metabolic pathways so chemical reactions such as cellular respiration as I mentioned before I already wrote down the equation of cellular respiration let me write it down again it doesn't hurt to see it again since you're going to have to learn it anyway so this is the chemical equation of cellular respiration however in cells this chemical th this chemical reaction doesn't take place in one big step rather is broken down in a series of chemical reaction kind of breaking it down in baby steps so that's what we refer to as metabolic pathways metabolic pathways can be l linear branched or cyclical in a metabolic pathway you start with the starting compound every time you see an arrow that represents a chemical reaction and then at the end of that chemical reaction you have a product the second reaction is this product from the first reaction now will be the substrate or reagent of the second reaction and will undergo a second chemical reaction to produce this product in the last step this Pro this product will now be the reactant or substrate and will be converted into the finer product in a linear pathway as you can see the the reactions take place in a linear sequence in a branch pathway uh one of the uh products or intermediates will have two different choices depending of the needs of the cell and in a cyclical pathway it goes in a circle in which some products are going to be released from the pathway uh doesn't matter which type of pathway we're talking about the starting compound is always called the starting uh reagent or reactant or substrate that's another substrate that's a synonym for reactant and the final product is called the the end product anything that is form in between that starting compound and the end product are called intermediates intermediates are transient they're not long LIF they're just made and then used made and then used now each one of those steps each one of those arrows or chemical reaction is catalyzed by an unique enzyme and we're going to be talking about enzymes now and enzymes are biological catalyst that means that they speed up chemical reaction these are agents that make sure that speed up chemical reactions they are proteins they are specialized proteins that have an unique structure uh structure within the enzyme that is called the active site and this is where the substrate of the reaction will bind and also where the reaction will produce in this case that substrate it split into two products the products are released and the enzyme is unchange that means that we can do this reaction all over again now enzymes are very very specific they recognize a substrate such as in a lock and key mechanism if the substrate um changes or it Mim it's if we have a compound that it's very similar to the substrate but it's not the actual substrate the reaction will not um will not proceed enzymes are not using the reaction they are just a platform where they facilitate the conversion of a substrate into product or products and the way that day speed of chemical reaction is by lowering the activation energy of chemical reaction um every chemical reaction out there must Supply an initial input of energy to those reactants it those reactants need to be energized when the reactants which are over here are now energized they reach this um pick over here which is called the highest energy state of a chemical reaction or the um or the transition state okay so at that point the reactants are very unstable and the reaction can proceed toward the products now that is a high jump to go all the way there so the way enzymes facilitate and make sure these reactions work faster is by lowering that bump so the red line over here represents the same chemical reaction catalyzed by an enzyme in that case now the chemical the activation energy is not that high doesn't need to go doesn't need to achieve that high and it's still very efficient for the reaction to proceed toward the products again the active site is the side where the substrate binds and the reaction takes place in a metabolic pathway in which we have a starting compound go to Intermediate A intermediate B and then the end product each one of those reactions is catalyzed by by a different enzyme now enzymes need helpers and those helpers are called co-actors and co-enzymes and this is a list of some important co-enzymes out there uh they participate in Redux reactions that means that they help in the transfer of electrons from a donor to a recipient and depending on the chemical nature of that helper we call it either a co-actor or a co-enzyme a co-actor is something very small it usually refer to ions such as zinc or Metals such as iron or sometimes there's a manganese or so on co-enzymes are larger these are organic compounds and some important co-enzymes are for example co-enzyme a fad NAD plus and so on and enzymes are very sensitive to the to their environment um they the because they're proteins that shape needs to be conserved in order for them to function uh properly so the most important factors to consider when stting enzyme are pH and temperature so each enzyme has their own Optimum temperature and their optimum pH these are the different profiles the first one is a temperature profile of studing enzyme activity the highest peak of that curve that's the best temperature at which that enzyme works works if that temperature is changed either lower temperature or higher temperature the activity of the enzyme decreases dramatically is most likely because that enzyme became denatured and if they lose their shape they lose their function this one shows um a pH profile the optimum pH is usually at the peak of that in that case it you it's it's a range so if the pH changes the activity of the enzyme changes dramatically another factor that we need to consider when studing enzyme is the soul concentration or the presence of ions in the vicinity enzymes are regulated uh this metabolic pathways are not always working all the time uh if is if especially if these Pathways have to do with building a metabolite there's going to be a point that uh we don't need to to do this all the time so enzymes can be regulated by different ways the most common ways is for allosteric control or allosteric regulation we already talked about an active site which is the site of of the enzyme in which the substrate or reactants bind but there is another side of the enzyme called the allosteric side this is the site where you can control an enzyme so even though it's not that molecule that inhibitor is not binding at the substrate when it binds to the allosteric side it changes the conformation of the active s so that the substrate cannot longer bind in there in the case of feedback inhibition the takes place in linear Pathways in which the very end product of the pathway is the allosteric inhibitor to the first enzyme of the pathway so that basically shuts down the pathway efficiently until the cell is ready to resume this activity there are different types of inhibitions in enzymes an inhibitor can be competitive or non-competitive competitive a competitive inhibitor is an inhibitor that competes for the active side of the enzyme they look very similar to the substrate for example in this enzyme the substrate is paba but a sulfat drug could be an inhibitor of that enzyme it looks similar to the substrate it is definitely not the substrate it can try to fool the enzyme into binding to the active site but the enzyme will not recognize the chemical groups of the of the inhibitor and the reaction will not proceed a non-competitive inhibitor that's a type of inhibitor that binds to the allosteric S such as the one that we saw in the previous slide