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Current time:0:00Total duration:12:02

Video transcript

so let's give ourselves an overview of glycolysis and glycolysis is an incredibly important biochemical pathway it occurs in in practically all life as we know it and it's all about taking glucose as a fuel and in the process of breaking it up ly sing the glucose glycolysis breaking it up into two pyruvate two pyruvate molecules glucose is a six carbon molecule each of the pyruvates are three common 3 carbon molecules in the process of doing that you produce two ATP's net it actually turns out that you need to use two ATP's and then you produce four so you use you use two ATP's that's often called the investment phase and we'll talk about in a second and then you produce you produce four ATP's for a net for a net of plus two ATP's and that's what we see right over here you see a planet of two ATP's being produced directly by glycolysis and then you also have you also have the reduction of nad to NADH remember reduction is all about gaining electrons and over here nad that's nicotinamide adenine dinucleotide we have other videos on that it's a it's an interesting molecule it's actually a fairly decent-sized molecule we see this positive charge but then we see that not only does it gain a hydrogen but it loses its positive charge so it gains a hydrogen and an electron you could think on a net basis it's gaining a hydride it's gaining a hydride now a hydride anion is not going to typically be all by itself but on a net basis you can think about that's what's happening and so it's gaining a hydrogen and an extra electron and so this the nad plus this is going to get reduced that is going to get reduced to NADH so this is getting reduced to NADH and that NADH once it's what it can then be oxidized in the electron transport chain and we'll study that later on when we think about oxidative phosphorylation to produce even more ATP's but on a very high-level simple basis glucose being broken down in pyruvate six carbons three carbons each of these pyruvates now there's other things attached to the carbons we'll see that in a little bit two ATP's net generated and you have the reduction of nad to NADH s and those can be used later on to produce more ATP s now glycolysis is typically just the beginning of cellular respiration if oxygen is around then you have these products some of these products moving into the mitochondria where you can have the citric acid cycle Krebs cycle and the oxidative phosphorylation occur if you don't have oxygen around then you're going to do anaerobic respiration or you're going to go into fermentation we'll talk about that in a future video and that's really about figuring out what to do with these products and especially replenishing your NAD+ now now that we have a very high-level overview of like glycolysis let's get a better appreciation for exactly what's going on and whenever I look at these more detailed more detailed processes the one thing to just appreciate is is how much complexity is occurring in in all of your cells right now this isn't some just well it is fairly abstract you just even imagine these things but this is happening throughout your body gazillions of times right now this isn't something that somehow distant from you it's also fun to appreciate well how all of this was discovered by scientists and so it's that's a whole other fascinating discussion but the whole point of this video is just gives their appreciation for the actual mechanism or the or the reaction by which it occurs I'm not going to go into the detail of organic chemistry mechanism so over here this is a glucose molecule over here you see one two three four five six carbons and then the first step is it gets phosphorylated and we have a whole video on the phosphorylation of glucose and all of these steps are facilitated with enzymes the phosphorylation is facilitated with the hexokinase kinase as a general term for an enzyme that either facilitates phosphorylation or D phosphorylate ordy phosphorylates it's it's dealing with phosphorylation I guess you can say and all enzymes are all about lowering the activation energy and the way that hexokinase is due or part of how they do it is they involve the cofactor magnesium ion and we've talked about that in other videos how cofactors can help an enzyme lower the activation energy and to do the phosphorylation we use an ATP so this is minus 1 minus 1 ATP so we are in the investment phase we are in the investment phase right over here but this reaction it strongly goes from left to right it's a coupled reaction that thinking that phosphorylating the glucose that that requires free energy but the ATP releases free energy you couple these reactions that strongly goes from left to right now what and just to be clear what happened this this over here got replaced or maybe I should say this over here got replaced with that over there just to keep track of what's happening now another enzyme catalyzed reaction this one is actually an equilibrium it can go both ways but as we'll see the right side or the the things that are further into the glycolysis process these are constantly being turned into further products so their concentrations are going to go down and so the reaction is will tend to go that way although this this particular reaction going from glucose 6-phosphate to fructose 6-phosphate this could be an equilibrium but the enzyme that facilitates this phospho glucose isomerase isomerases these are enzymes that help grow from one isomer of a molecule to another isomer and that's what's happening here instead of this oxygen being bound to this carbon this bond forms with this carbon and so you have fructose you have the 5 carbon ring over here or you have the 5 element ring you have 4 carbons in it versus a 6 element ring where right over here you have five carbons so this bond goes to this carbon right over here and that's the main difference and then you have another very strong forward reaction once again facilitated by ATP and this is done by phosphofructokinase it says the word kinase in it and using up the ATP you can guess what's going to happen we're going to attach another phosphate group to the fructose 6-phosphate and now you have two of these phosphate groups so so this this hydrogen right over here is now replaced with another with another phosphate group and once again it's facilitated by the magnesium cofactor it helps stabilize some of the negative charge associated with the phosphate groups we talked about that in other videos but the important thing is it uses another ATP we're still in the investment phase negative one negative one ATP and every time I look it's just fascinating that all of this stuff is happening in your cells as we speak in fact in order for me to speak this has to happen because my body needs to take glucose and come up with some energy to turn two ATP's so that I my muscles can actually move and I can actually inhale and exhale and all the things I need to do for speech so appreciate what's going on over here now the next step we talked about the whole problems the whole process of glycolysis is lysine glucose and over here this is a dirt this is derived from glucose and some phosphate and the next step we're actually going to break it up and we're going to break it up using the enzyme fructose biphosphate aldolase aldolase enzymes they facilitate the aldol reaction this in this one we're going to actually the aldol reaction could be to merge two to put together two molecules or in this case we're going to break them up and we break them up into two 3-carbon chains now these two three carbon chains glyceraldehyde 3-phosphate and this character right over here they can be converted between the two with another isomerase this triose phosphate isomerase right over here so at this point in glycolysis we can think of ourselves as really having two of these so let's say two times glyceraldehyde 3-phosphate so as we go further on just imagining this happening twice for every glucose molecule and at any time you get confused I encourage you to pause the video and see how these pieces and these pieces put together can form that over there so now we have another reaction it's facilitated by Adi Hite dehydrogenase dehydrogenases usually are involve in this case this is this is this is the reduction of nad we saw that in the overview video so nad is being is being reduced and this can be used this NADH later on can be used in the electron transport chain to potentially produce some more ATP but in that process in that process we also add another phosphate group to the glyceraldehyde 3-phosphate so you see this phosphate group you see this phosphate group right over here that wasn't that wasn't here that wasn't there before that wasn't there before and actually this right over here is I should I should I should have arrows on both sides this right over here that reaction could actually go both directions actually that reaction can as well and then and then we we we are now going to be in the payoff phase so this right over here we're starting with this molecule that has these two phosphate groups and then using the the phosphoglycerate kinase we're able to pop one of those phosphate groups off and in the process produce ATP produce ATP now we might want to say plus one ATP but we have to remember this is now happening twice because we had two of those glyceraldehyde 3 phosphates so now we could say if we're if we're talking about this happening twice two plus two ATP's we are now in the payoff phase then you have facilitated by the phosphoglycerate mutase a mutase is a class of isomerases i have trouble saying that that'll take a functional group from one place to another or take put one part of a molecule to another part and you see this phosphate group you see this phosphate group moving on from this carbon to the middle carbon and so that's what that's doing then we use an enol ace to get over here and then the pyruvate kinase the pyruvate kinase and here the kinase is going to be used to dephosphorylation right over here and it gets us to the way i've drawn it is pyruvic acid since i've drawn I have the hydrogen here and if the hydrogen is let go and this oxygen hogs the electron we would call this pyruvate and this is considered to be the end of I guess you say mainstream glycolysis but what happened and and and and I don't want to glaze over what happened over here this ADP got converted to another ATP but it's going to happen twice so this is another plus two ATP's so hopefully you see the investment phase we use an ATP right over here to phosphorylate the glucose we use another ATP right over here to throw that second phosphate group on the what was this the fructose 6-phosphate but then we get the payoff phase so we're able to produce this NADH and this is actually going to be two NADH s because everything here is going to happen twice now we can assume that this character over here also gets gets converted to a glyceraldehyde 3-phosphate and now we produce two ATP's because this is happening twice and we produce two ATP's right over there so hopefully everything we talked about in the beginning everything we talked about the meting actually makes sense
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