hello organic chemistry students in this video we're going to talk about the biochemical pathway called glycolysis now glycolysis is going to start with glucose and end up with a new mystery compound I'll go ahead and give you the sneak preview it's called pyrates now where does glycolysis occur now unlike the electron transport chain and the kreb cycle which both occur in the Matrix or on the inner membrane glycolysis actually occurs in the cytoplasm of a cell so remember the alien um picture of a of a cell that I normally draw here's our nucleus here's our mitochondria this stuff all out in here is the cytoplasm so glycolysis is in the cytoplasm of the cell why is that important since it's not localized in the mitochondria and dependent upon the ETS oxygen is not requ required for glycolysis to run so with or without oxygen glycolysis operates completely by itself it does not matter if oxygen is present that'll be important for us now the etss and kreb cycle are also not required so no matter what the glycolysis pathway will always run no matter what else is happening inside a cell so let's look at this pathway right here now you have a picture of this present in the module page highly recommend printing it off and putting in the or um filling in the different substrates along the way to form our pyate molecules notice what I'm saying molecules we not just forming one we're forming two per glucose let's go ahead and get into this now in this reaction we're seeing a lot of equilibrium arrows these equilibrium arrows right here is going to allow us a lot of control on how this reaction proceeds now the big reaction of fructose 65 phosphate to fructose 16 diphosphate is a key regulatory step of glycolysis and our body will use this if we have extra ATP it will slow down glycolysis and thereby Krebs and electron transport by modulating and inhibiting this step right here but we're not going to get into that into this video right here we want to talk about the basic metabolism of glucose in a Cell now before I show the first reaction glucose right here it can be actively transported into the cell via glucose Transporters but it also diffuses from a cell so it's going in and out in and out now we don't want that if a cell needs energy it has to have a way of trapping the glucose inside and welcome to Step One of glycolysis so in step one of glycolysis our glucose molecule is going to be phosphorated at the sixth position right here with with ATP so we are using ATP we are now deficient one ATP molecule we have phosphorated the six position what does that mean this glucose 6 phosphate cannot leave the cell by phosphor it so cannot leave the cell by phosphor it we've trapped it inside the cell that needs energy that is important now glucose is an Aldos type of carbohydrates so here's an Aldos the next step is taking this Aldos and converting it to its ketos fructose counterpart so the aldhy at Carbon one will become an alcohol the Ketone or the alcoholic Carbon 2 becomes a ketone in fructose and we form our five membered fructose 6 phosphate and there's no energy required here no massive amounts of steps going on this occurs relative rapidly in an equilibrium process the important thing to notice we use one ATP to trap the cell or the Trap ATP within the cell and now we can go back and forth between these two molecules now with fructose 6 phosphate the next thing that we are going to do which is going to seem absolutely crazy is we're going to use another ATP now glycolysis is being run because we need ATP why on Earth are we consuming it we have to make sure the molecule doesn't leave the cell now putting two phosphate groups on seems a little over redundant and we're going to see in the next step why we put another phosphate on so from fructose 6 phosphate which is the same as this structure right here let me go ahead and circle the phosphate group so we can represent them as a true phosphate here it is oops here it is right here connected of the oxygen that's shown there that's what fructose 16 diphosphate looks like the next step is an enzyme called an aldolase alol as comes in and breaks the carbon 3 to carbon 4 Bond and what we end up getting is dihydroxy acetone phosphate from the top part of the molecule and glycer alide 3 phosphate from the bottom part of the molecule let's notice some key characteristics both of these fragments have phosphates on them which means they can't leave the cell so why did we put the second ATP on it's for this step right here if we didn't do this step here once we cleave this molecule the glycer aldhy 3 phosphate or the glycer alide would leave the mo would leave the cell we don't want that we want it to remain inside the cell and that's why the second ATP is used so we've now formed dihydroxy acetone 3 phosphate and glycer aldhy 3 phosphate now that's what I'm showing you right up here just as a little reminder the glycer aldhy 3 phosphate this alahh is oxidized to a carboxilic acid and we put an inorganic phosphate group on it so an NAD oxidizes the aldhy to a carboxilic acid and we put a phosphate group on it we've just formed formed 1 NAD that's important plus 1 nadh excuse me I was saying NAD I meant nadh in the Second Step the 13 diphosphoglycerate we're going to clip off the phosphate group that we just put on Via the oxidation process and we're going to form an ATP this is the first time we're seeing ATP formed outside the electron transport chain minus that one step in the KB cycle this is what we call substrate level phosphorilation I don't think there's an o in there but I'm going to put it in there I'm a horrible speller if you haven't known this already so we form an ACP via a substrate level phosphor relation event so now we've just formed one ACP we just formed one one ATP what's the important thing here we've consumed two atps we finally just kicked back one of them so we're now only down one but if the nadh goes to the mitochondria inside the Matrix we're going to form three ATP we're now up a net 2 ATP this is going to be important in a little bit now the three glycerol phosphate is going to take this phosphate and actually isomerize it to the second carbon this is going to create a high energy intermediate our body does this all the time it will create high energy intermediate so when it breaks down we can harvest the energy from it and the two phosphoglycerate becomes phospho enop pyate we form a double bond between these two carbons via a dehydrogenation reaction now this phosphate on this carbon carbon double bond is highly unstable so an ADP comes in takes the phosphate off and forms ATP giving us an O on a carbon carbon double bond which immediately tzes to a carbon oxygen double bond just like we learned in alkine chemistry so what just happened we just formed another ATP in this process so if we're looking at ATP formed directly from glycolysis we use two atps to start we just formed to atps we're at a net zero right now wonderful the nadh if we're under aerobic conditions goes down to the mitochondria we form 3 ATP we're up three that's wonderful news but now let's look at the big picture here we just talked about using two atps one here one here forming an ATP here forming an ATP here at the end and that creates our Net Zero why am I saying Nets net means after all expenses are occurred or paid back what did we get at the end so when a glucose molecule enters glycolysis what comes out I'm saying two pyrites two pyrates two at sorry four atps two nadhs but two were used so the overall gross is 4 atps and a net of two atps this should seem weird wait a second two pyrates coming out no it doesn't let's go back and look at the cycle once we're right here at fructose 16 diphosphate when it breaks down via the alas we form glycer aldhy 3 phosphate which forms an nadh forms an ATP and then coming through forms another ATP to form pyrate we're now Net Zero ATP what about the dihydroxy acetone 3 phosphate once the glycer alide 3 phosphate is consumed the dihydroxy acetone 3 phosphate isomerizes to the glycer aldhy 3 phosphate forming another nadh forming another ATP and forming one more down below and that's where we get a grand total of four atps two nadhs are formed per one glucose and two pyrates we use two so the overall gross is that we're forming four atps but the net once we pay back back the two glucoses or the two atps that we used at the beginning are we get four excuse me two atps right here what else do we form we get two atps we also get two nadh's so right now just from glycolysis we're getting a net of two atps for every time glycolysis runs that's great the kreb cycle doesn't give us any ATP directly right none whatsoever glycolysis gives us 2 ATP if oxygen is present the nadhs can go inside the mitochondria inside the Matrix form three atps per nadh for a new 6 ATP for a grand total of 8 ATP from one glucose molecule now this is if O2 is present wow that looks horrible now if there's no Oxygen present the ETS can't operate right so all we're going to form is 2 ATP two is better than none so now let's think about the big picture we have talked about in the so far we've talked about in this class using the electron transport chain to take nadh's and fadh to pump it into the etss and form ATP wonderful we've talked about acetal Co entering the kreb cycle it goes around this cycle right here and what do we form nadh's and fadh2s we just talked about glucose forming two pyate molecules in this process we're going to consume two atps we're going to produce four atps and two nadh's which can go down to the electron transport chain so if oxygen is present one glucose will provide four ATP two nadh's goes through the electron transport chain the net over here is a grand total of two plus 6 more is 8 atps so we have eight atps if oxygen is present that's what this red is right here if oxygen now now the acetal co-s per one acetyl Co we get 12 ATP that's wonderful we have a small problem right now how does the pyate become a cetal COA and I forgot to write the COA right here and that is what the next video is going to talk about when we finally wrap up how ATP formation and production occurs in our body we are going to explore this Gap right here how does pyate become a cetal COA or does it and what is the actual number of ATP that we form per one glucose molecule under aerobic conditions as always highly recommend you go back watch this video again take notes off it off of it print off the blank metabolic cycle that I've provided within the module and fill in the different steps here if you have any questions please feel free to email me come come to my office hours or recitation section and I'll be happy to help you however I can I hope each of you are doing well and I look forward to seeing you all in lecture soon have a wonderful day