okay so today we're going to cover chapter eight which is microbial metabolas so metabolism is essentially all the chemical reactions and the physical workings that are current side of the cell and when we look at metabolism there's two processes that can occur anabolic reactions and catabolic reactions anabolic reactions is when you have biosynthesis and this is when you make uh the synthesis of cell molecules and structures typically from smaller subunits whenever you undergo an anabolic reaction this is going to require the input of energy okay so this is going to cost you energy an example of an anabolic reaction would be that of protein synthesis where you take something like amino acids and you link them up together to make a functional protein the second type of metabolic reaction is a catabolic reaction and with catabolic reactions you are breaking down larger molecules into smaller subunits an example of this would be say breaking down a glucose molecule for the release of energy and to be converted into an usable energy in the form of atps typically when you under catabolic reactions this will release energy so you will end up producing or converting to a usable form of energy okay now the accomplishments of metabolism is that it assembles smaller molecules into larger macromolecules for the cell and this will utilize ATP such as an anabolic reaction or it can degrade macromolecules into smaller molecules which is a process that will yield energy such as a catabolic reaction it will collect and spend energy in the form of ATP or heat and this is essentially how the energy will get converted to so when we undergo a catabolic reaction of breaking down a glucose molecule we will end up producing anywhere from 34 to 38 atps and the other thing that we will end up producing or releasing is heat now unfortunately heat is not going to be a usable form of energy and it is oftentimes lost so here's a simplified model of metabolism here we have nutrients from outside of the cell or from internal pathways we'll undergo catabolic reactions which can include things like glycolysis the Krebs cycle the electron transport chain or potentially even fermentation if it's an anaerobic anaerobic pathway this will end up yielding energy it will also give you precursor molecules which now can be used for anabolic reactions such as the building blocks to make proteins larger sugars a new good nucleic acids or fats and the cell can even continue to use this for anabolic processes and eventually you can even you know maybe form a whole new cell by cell division um so this is sort of a simplified model of what's actually happening here now enzymes are going to be the Catalyst uh that will actually fuel chemical reactions of life catalyst is going to speed up the rate of a chemical reaction without actually becoming part of the products or being consumed in the reaction enzymes are biological catalysts enzymes are made up of proteins and what enzymes do is they overcome the activation energy allowing the reaction to proceed by increasing the thermal energy or Heating to increase the velocity of molecules also increasing the concentration of reactants to increase the rate of molecular collisions adding a catalyst will speed up the overall reaction so what's a sort of quick little checklist here of different types of enzyme characteristics most enzymes are composed of a protein they may require cofactors which could be non-protein components they will act as organic catalysts which are required to speed up the rate of cellular reactions they speed up the rate of cellular reactions by lowering the activation energy which is required for the chemical reaction to proceed if you need characteristics such as shape specificity and function these are proteins so the substrates that these proteins will bind to are extremely specific they will enable metabolic reactions to proceed at a speed that is compatible with Life they have an active site for Target molecules this is the place where these substrates will bind and again this binding will be a very specific binding they are much larger in size than their substrates they associate closely with substrates but do not become integrated into the reaction product what this is stating is that enzymes will never become part of the product they are this there to facilitate the overall reaction they are not used up or permanently Changed by the reaction and in fact they are oftentimes recycled thus the function in extremely low concentrations meaning you don't have to have a huge number of enzymes produced to accomplish metabolic pathways because they are recycled and an enzyme can undergo many many many uh chemical reactions enzymes can be greatly affected by both temperature and pH what happens is if you go too high on the temperature you could denature the proteins which will make the enzyme inactive her pH if you go too basic or too acidic on either end of the spectrum you will denatur the proteins and they will become inactive enzymes can also be regulated by feedback and genetic mechanisms so how do enzymes work the substrate these are the reactive molecules upon which the enzymes will act the enzyme binds to the substrates and participates directly in changes to the substrate keep in mind they do not become part of the products it is not used up by the reaction and they can function over and over again so the overall structure of enzymes you have the protein molecules simple enzymes consist of protein alone uh conjugated enzymes or Hollow enzymes this contains the protein and some other non-protein molecule foreign these are protein portion of the enzyme the cofactor could be the non-protein portion such as an organic or an organic molecule and coenzymes are organic cofactors such as um sorry there are organic cofactors so the actocyte or the catalytic site this is the actual site where the substrate binds it is a three-dimensional crevice or Groove that is formed by the way amino acid chains are folded each enzyme has a different primary structure variations in how the protein will fold and a very unique active site which will sequester very unique and specific substrates okay again you want to think about the fact that enzymes are proteins whatever you're talking about proteins you're talking about very specific binding sites and we see that here okay uh and here's just a little kind of cartoon to show you that you can have many substrates the only one that's going to fit in is the one that fits in perfectly um I'm sure you guys remember talking about you know receptors and the substrates that bind them it's the same deal here uh oftentimes used to describe receptors as like a lock and key same thing here if you have a mutation in the enzyme that can actually affect the functionality of the enzyme and it might not actually be able to bind the substrings anymore all right so the cofactors metal ions and coenzymes metallic cofactors could be examples could include iron copper magnesium manganese zinc Cobalt selenium they assist with the precise function between the enzyme and the substrate they can activate enzymes they can help bring the active site and substrate close together they can participate directly in chemical reactions coenzymes these are organic compounds that work with the alpha enzyme to alter the substrate they remove a chemical group from one substrate and add it to another substrate and they carry and transfer hydrogen atoms electrons carbon dioxide and amino groups vitamins are an important component of coenzymes there are six classes of enzymes you have oxa reductases which transfer electrons from one substrate to another and dehydrogenases which will transfer hydrogen ions from log compound to another transferasis Diesel transfer functional groups from one substrate to another Hydro laces will cleave Bonds on molecules with the addition of water liases will add groups or remove groups from double bonded substrates isomerases will change a substrate to its isomic form and ligases will catalyze the formation of bonds with the input of ATP and the removal of water and again these are the six different classes of enzymes that we typically see associated with metabolic pathways some sample of enzymes they're substrates and their reactions so for example if we look at lactase this will actually hydrolyze lactose which means that it is breaking lactose down into glucose and galactose glucose will then go on to be oxidized and catabolized uh even further uh the actual name of lactase is beta d galactosidase That's a system systematic name so here you just see an example A lot of times what will happen is these uh enzyme names are going to tell you actually what it's doing okay uh transfer reactions by enzymes these are accomplished by oxide reductases and this brings us to what we call redox reactions or oxidation reduction reactions and a lot of metabolism is based off of redox reactions an oxidation reaction is a reaction in which you lose electrons and this is when that compound that loses the electrons is now referred to as oxidized a reduction reaction is when you gain electrons and a compound that gains electrons is referred to as reduced NAD and fad are coenzyme carriers these are what we refer to as electron carrier proteins their job as you'll see when we get to the actual Pathways is to actually pick up the electrons that end up getting released and transfer them to another source or another molecule NAD and fad will never be final electron acceptors they are only electron carriers we'll talk about that again a little bit more when we get to the actual pathways location of enzymatic activity location of enzymatic activity could either occur on the outside of the cell or on the surface of the cell this is referred to as EXO enzymes or can occur inside the cell which is referred to as an endo enzyme enzymes can either be regulated where they are turned on or turned off in response to some type of stimulus constitutive enzymes these are enzymes in which they are always sort of quote unquote turned on meaning that you're always present in a relatively constant amount regardless of the cellular environments a lot of things that the cell means all the time would be considered operated by a constitutive enzyme wow so the role of microbial enzymes and disease pathogens and secrete unique exoenzymes that have helped them to avoid host defenses or promote multiplication in tissues they are considered virulence factors or toxins because they contribute to disease and when we get to unit 4 of this course and we talk about virulent cut conference factors you'll see that these digestive or EXO enzymes play a huge role so for example if you had a bacteria that was secreting enzymes that break down keratin such as carrots and Ace and collagen which breaks down collagenase or sorry collagenase which breaks down collagen you can imagine that that bacteria by secreting those enzymes could actually cause damage to skin which is primarily composed up of keratin and collagen now enzymes are proteins again cycling back to that main thing there because enzymes are proteins they can be denatured weak bonds that maintain the shape of the apple enzyme are broken by heat low or high pH or certain chemicals disruption causes Distortion of the enzyme shape this prevents the substrate from attaching to the active site and non-functional enzymes will block metabolic reactions and can lead to cell death okay okay sorry about that so metabolic pathways how do enzymes play a role with metabolic pathways metabolic reactions most often occur in a multi-step series or pathway each step is catalyzed by an enzyme the product of one reaction is often the reactant or substrate for the next action many Pathways have branches that have alternate methods for nutrient processing some Pathways can take on a cyclical form and pathways are interconnected and merge at many different sites so here you can see you can have a straight up linear pathway you can have cyclical pathway then you can also have branched Pathways where they diverge or they converge for example here you might have two amino acids uh that have different starting points but ultimately end up with the same endpoints so direct controls in the action of enzymes we have either what we call competitive inhibition or non-competitive inhibition a molecule that resembles the substrate and occupies the same active site as the substrate and prevents the substrate from binding as referred to as a competitive inhibitor the enzyme cannot act on the inhibitor as is effectively shut down non-competitive inhibitor what happens here is instead of the inhibitor binding to the same active site as the substrate the non-competitive inhibitor will bind to some other site on the protein which is referred to as an allosteric site and by binding of that inhibitor to the allosteric site what happens is it changes the shape and structure of the protein making up the enzyme when that occurs the active site is no longer in the same position and shape as it was was because the active site now changed shape the substrate is not able to bind and you inhibit the enzyme so again here is a competitive inhibitor here's a normal substrate here's the competitive inhibitor what happens is the competitive inhibitor binds the same active site and the reaction is blocked here for non-competitive inhibitor here we have the substrate binding to the active site but in this case what happened was the inhibitor bound to an allosteric site and when that happened the reaction is blocked because binding of the regulatory molecule in the allosteric site changes the conformation the active site so that the substrate cannot bind either enzyme repression this stops the further synthesis of an enzyme somewhere along its pathway if the end product of the enzymatic reaction reaches excess the genetic apparatus will for replacing enzymes is suppressed the response time is longer than for the feedback inhibition and it affects more or more enduring for enzyme induction enzymes appear or are reduced only when suitable substrates are present the synthesis of the enzyme is induced by its substrate inverse of enzyme repression okay and recording one will stop here with the conclusion of enzymes and we will now move on to actual energy in cells and the metabolic pathways that produce them