Metabolism | Pentose Phosphate Pathway

hi ners in this video we're going to talk about the pintos phosphate pathway now the pintos phosphate pathway is a very very important pathway and um what's going to happen is we're going to see exactly how important it is throughout the series of this the series of this uh video but it's going to be extremely extremely important for synthesis reactions for example synthesizing neurotransmitters synthesizing lipids cholesterol synthesizing nucleotides you know synthesizing many many different types of things so we're going to see that this is a very very important step also it's very very important for

free radical reactions so we'll see exactly how all this is happening now if you guys remember let's say I bring glucose into the cell right so I bring glucose I'm going to represent with a G I'm bring this into the cell but you know that it can't just pass through the cell membrane you know it has to have a special type of glutch transporter right so let's just say that this is a liver cell if it's a liver cell you know that the liver cell has glut two Transporters so let's say that this is a

liver cell and this is having glut two Transporters but whatever okay we bring this glucose into the cell once we bring this glucose into the cell so now let's say here's our glucose if you guys remember glucose can be acted on by a special enzyme present with inside of the liver and it's a special one right that enzyme is called glucokinase so the enzyme here is called gluco kinas now glucokinase is doing what it's putting a phosphate on the six carbon of glucose so let's now do that let's actually represent that so now what's going

to happen we're going to have glucose here but if you guys remember in this step what are we going to do we're going to take ATP and convert it into ADP because this glucokinase is going to take and transfer one of the phosphates off of the ATP onto the glucose so now on the six carbon of glucose I have a phosphate group so this is my glucose six phosphate so now what am I going to do with this glucose 6 phosphate well there's two things I can do with it one thing is I could run

this puppy through glycolysis right I could run this sucker right through glycolysis so let's run it through glycolysis really really quickly ready so what are some of the steps of glycolysis if you guys remember I can take glucose 6 phosphate convert it into fructose 6 phosphate then if you guys remember from that fructose 6 phosphate I can then then do what I can convert that into fructose one six bis phosphate so in this step I can convert fructose 6 phosphate into fructose one six Biz phosphate but remember this step required ATP so ATP is being

utilized in this step and we're converting this molecule now into fructose six bisphosphate okay six bisphosphate then what happened if you guys remember the fructose 1 six bisphosphate split by an aldela enzyme right and got converted into dihydroxy acetone phosphate and glyceride 3 phosphate and then you know that these guys can iSeries between each other right then the glyceride 3 phosphate did what it went through a series of reactions like what it went to 1 comma 3 BPG to what then it actually went to three phosphoglycerate to two phosphoglycerate to phosphoenol pyruvate to pyruvate and

it just keeps going and going and going right but throughout a series of these steps you guys remember that you generate what you generate an ATP you take an ADP here and you make ATP but this happens twice because when you split fructose one 16 bis phosphate you get one of this guy and one of this guy but most of it funnels into this guy so technically you have two of him two of him two of him two of him two of him and two of him so technically I generate two ATP in this step

another thing is right here going from 1 three bis phosphoglycerate bis phosphoglycerate to three phosphoglycerate I also generate another ATP but again two of them because this pathway occurs twice so in general how many ATP did I produce out of all of this I produced four ATP right but that was the gross ATP because I used two ATP in the beginning of the process I actually only netted really two ATP so I only really netted two ATP okay now this is going to be important that we understand that this glucose 6 phosphate can go through

this pathway just depends upon the body's needs now we're going to take this puppy and run it through the pentos phosphate pathway because I want to show you how the glycolisis pathway and how the pentos phosphate pathway are so intertwined and interconnected so now look this is an important step I am going to make this step blue this step right here is extremely important okay so in this step here I'm going to take glucose 6 phosphate and I'm going to convert into a really really funky name I I hate that they call it this but

it's guess is how it is it's called six phospho glucono lactone now that's a mouthful right but again what is this molecule here called it's called six phosphor glucono lactone what happens in this step is going from glucose 6 phosphate to six phosphor gluconolactone I'm going to reduce the glucose 6 phosphate so in order for me to reduce him what kind of molecule would I need in order for this to uh I'm sorry actually I'm not reducing glucose 6 phosphate I'm oxidizing glucose 6 phosphate so I need a special molecule a special molecule in this

step is going to be in a DP positive I'm going to take this nadp positive across this step and you know what he's going to do he's going to pick up some hydride ions you guys remember hydrides hydrides are just basically me saying I have a hydrogen with a proton and two electrons right with an overall kind of a negative charge there that's a hydride that's what a hydride is it's a proton with two electrons he's going to pick up some hydrides from the glucose 6 phosphate and get converted into six phosphor gluconolactone now in

order for that to happen if you guys remember anytime you see NAD or nadph always remember that there is a dehydrogenase enzyme there so this enzyme here is going to be extremely important he is called glucose six phosphate dehydrogenate so again this enzyme is called glucose 6 phosphate dehydrogenase extremely important enzyme because this is going to be one of the enzymes that determines whether this glucose 6 phosphate goes into six phospho gluconolactone and we'll talk about that when we discuss regulation now the six phosphor gluconolactone can then go into another step look what's going to

happen here I'm going to take this six phosphor gluconolactone and I'm going to convert it into another molecule but specifically all I'm going to really do in this step is I'm just going to add some water so I'm going to add some water in this step and I might get out of proton as a result but either way I'm just adding some water into the step it's not really that important of a step but I just want to mention it and again this is actually going to be called six this one's a little easier phospho

gluconate so what happens is I take six phosph gluconolactone add a little bit of water into the step and get six phosphogluconate now six phosphogluconate whenever I form him I'm going to go into this really really important step here in just a second now if you want to know this enzyme you can it's called lactonase so it's called lacto don't get that confused with lactase that's an enzyme that actually converts you know lactose into glucose and galactose but now what I'm going to do is is I'm going to take this Latinas enzyme I'm going to

convert six phosph gluconolactone into six phosphogluconate now I'm going to go on to another important step in this next step let's actually do the step in pink this is another important step here I am going to generate another set of nadph is here so I'm going to take another nadp positive and convert it into NPH now to clarify something glucose 6 phosphate is six carbons so let's put that right up here above it six carbons so this is a six carbon m molecule six phosph gluconolactone is a six carbon molecule six phosphor gluconolactone is a

six carbon molecule this next molecule that we're going to talk about is called when six phosphor gluconolactone is acted on by nadp positive to nadph I'm going to form a molecule called ribulose 5 phosphate now when I form ribulose 5 phosphate this is important and the reason why this one is important is because he's going to get ready to turn into another molecule that we use for a lot of different processes like synthesizing nucleotides synthesizing DNA synthesizing RNA synthesizing nads and fads and co-enzyme we'll talk about and we'll list it but this carbon ribulose 5

phosphate is a five carbon molecule so what does that mean if I went from a six carbon molecule to a five carbon molecule that means I lost a carbon in the form of CO2 so there was some type of decarbox reaction decarbox you know decarbox is just basically when you're removing a carbon in the form of CO2 just like carboxy would be add adding in a carbon in the form of CO2 or sometimes even bicarbonate okay now we got this rulos 5 phosphate there's two fates of this rulos 5 phosphate oh what is the enzyme

that catalyzes this step this step right here is catalyzed by six phospho gluconate dehydrogenase now this enzyme isn't as important as glucose 6 phosphate dehydrogenase this enzyme is important nonetheless but it is not as important or not as significant as compared to glucose 6 phosphate dehydrogen there's a condition that we'll talk about uh with respect to this glucos uh glucose 6 phosphate dehydrogen if he's deficient it can lead to a certain type of hemolytic anemia with hindes body formation all right this ribulose F phosphate what can happen with this ribulose F phosphate I can take

this ribulose 5 phosphate and I'm going to have two Fates for it one fate is going to be for the formation of two different molecules but it depends upon the enzyme now ribulose 5 phosphate if it's acted on by a special enzyme and this enzyme is is an isomerase enzyme so let's say that there's an isomerase you know all isomerases are doing is they're just shuffling different carbons around so for example I can shift ribulose to another molecule and this new molecule that I'm going to form is called ribos five phosphate okay so now I'm

going to have my ribos 5 phosphate and then I'm going to have my ribulose 5 phosphate all I'm doing is I'm switching around different types of atoms for example this ribulose 5 phosphate can actually be converted into another molecule you know this molecule is called ribos fi phosphate now the only difference between ribos 5 phosphate and ribulose 5 phosphate is all all I'm doing is I'm switching you know ribulose 5 phosphate is in the Ketone form you know Ketone is basically when you have a carbon here let's say I have a carbon here and it's

got a double bond oxygen it's in between two carbons this is a ketone so this has a ketone form whereas ribos is a alahh so you know alahh they're specifically having a carbon double bonded to an oxygen with another carbon and then on the other part they have a hydrogen all I'm doing is I'm us utilizing this enzyme which is called an isomerase to switch the Ketone to an aldah that's all that's happening here so nothing crazy I'm just shifting around a little bit um with these oxygens right just shifting around a little bit so

I'm I'm shifting a ketone into an aldah now this other one is extremely interesting we'll talk about this more in organic chemistry but this enzyme is called a epimerase so it's called for example this is ribulose f phosphate isomerase this is ribos f phosphate epimerase but specifically on the third carbon so it's actually occurring on the third carbon now I'm G I'm going really really dumb this down because we're going to talk about it but what we're going to make now is as a result of taking this epimerase enzyme and converting ribulose 5 phosphate I'm

going to convert this into zulos five phosphate now what is the difference between ribulose 5 phosphate or I'm sorry between ribos 5 phosphate and xylos 5 phosphate really because when I'm taking this guy and converting it into ribos 5 phosphate I'm just having an isomerization reaction when I'm taking ribulose 5 phosphate and converting into zylos 5 phosphate I'm utilizing this epimerase enzyme now epimers are basically what's called diamer like I said we'll talk about this more in organic but this is called a DI aamer what it means is that they different and chir it in

one carbon so for example let's say for example on the third carbon so let's say that on the third carbon the fourth carbon and the fifth carbon of this molecule versus the third carbon fourth carbon and fifth carbon of this molecule let's say that the ribulose FI phosphate was R meaning that it rotates to the right I'm sorry clockwise this one rotates counterclockwise and let's say this one rotates counterclockwise if they were complete what's called animers this stereo centers would invert and they would turn into srr but the difference is is that these are not

an animers they're diamer so they differ in only one stereo Center so for example instead of them being let's say they're RSS this would be rrr the only stereo Center that they're now differing in with respect to each other is now going to be this third carbon they're going to have the same point there but they're going to now have these carbons being the inverted form okay so they're diers they're not completely ananur they're differing in one stereo Center okay anyway that's enough for the organic part of it now what I'm going to do is

I'm going to take these two molecules and I'm going to fuse them together that's what I'm going to do here I'm going to take the zylos FI phosphate and I'm going to take the ribos F phosphate I'm going to fuse these two together when I do that I'm going to have a special enzyme working on these two guys this enzyme we're going to call a transketolase enzyme so this is going to be called a trans ketas enzyme you know what's special about trans ketas enzymes they have thiamine pyrophosphate as a component of them you know

thyine pyrophosphate is one of the vitamins it's a very very important vitamin right so thomine vitamin B1 is very very important in this step because it's going to act as a co-enzyme the thyine pyrophosphate what's happening is trans ketolase is going to transfer a two carbon so it's transferring two carbons I know it might seem funky the way I remember it but it helps me I like to think that a ketone is in between two carbons so it helps me to just just simply being able to remember that this guy's transferring two carbons so he's

going to transfer two carbons so what happens is I'm going to transfer this ribos 5 phosphate let's say I take two carbons from him and I transfer it onto the zylos 5 phosphate so I'm going to lose two carbons from him so he's going to go from again this is five carbons this is five carbons here nothing changed all I did was I had isomerization and epimerization this five carbon and this five carbon I'm going to transfer two onto him and he's going to gain two that means he'll turn into a three-carbon fragment that three

carbon fragment is called glycer alide I'm going to put glyceride 3 phosphate we're just going to abbreviate it here so again this is called glyceride three phosphate that's one product of this reaction so one product is going to be glyceride three phosphate now this one gains the two carbons so he transfers two carbons onto the xylos phosphate and the xylos FI phosphate gets converted into what's called sedulo heptose 7 phosphate oh sweet goodness okay so sedulo hepto 7 phosphate is now formed and it's easy to think you know because it's by coincidence that the number

that the the phosphates on tells you how many carbons there is so for example ribos phosphate it just so happens to be five carbons xylos 5 phosphate just so happens to be five carbons glyceride three phosphate just so happens to be three carbons sedulo hepto 7 phosphate just so happens to be seven carbons but we know that because this was five this was five and all I did was I transferred two carbons from him to him okay now what can happen is this glyceride 3 phosphate has two destinations one is you guys have probably recognized

that these are the two same molecules so what can happen with this glycero 3 phosphate depending upon the body's demands which we'll talk about he could technically get fed into the glycolytic pathway let's show that here so technically this guy could get converted right here he could actually be fed into glycolysis if we need to okay or he could be involved in glucon neogenesis it just depends upon the body's demands which we'll talk about because glucogenesis we can make glucose glycolysis will go and make ATP okay but let's say that we don't need that we

need to do something else let's say we need to make we need to do another process so now what I'm going to do is I'm going to take this glycero 3 phosphate and I'm going to combine it with the sedulo hepto 7 phosphate so now I'm going to fuse these two guys together so now this guy here and this guy here are going to react okay what happens here there's another enzyme let's do this one in a different color let's do this one in black this is going to be called a trans alalas and this

one is going to be transferring three carbons so again I just like to remember Ketone it's in between two carbons so transfers two carbon fragment as default out transfers three carbons okay so what is he going to do well he only has three carbons so he can't lose them this guy has seven he can definitely donate so what he's going to do is he's going to take three carbons from this guy and transfer on to glyceride 3 phosphate so then what happens to the glycero 3 phosphate well he gains three carbons when he gains three

carbons he turns into another familiar molecule that I know you guys have heard of called fructose six phosphate where have we seen fructose 6 phosphate before I know I've seen it in glycolysis so where can this go then it can get fed up into fructose six phosphate so we'll just show like this for right now it can get fed into the glycolytic pathway but depending upon the body's needs it might go somewhere else but when the sedulo hepto 7 phosphate when there's the three carbons transferred from him he loses three carbons so what happens to

him then he loses three carbons and turns into a four carbon molecule that four carbon molecule is called arthos for phosphate okay now you guys can imagine fructose 6 phosphate just by coincidence there the phosphates on the six carbon how many carbons will he have then he will have six carbons and again this is just by you know coincidence that all this is happening but it's it's nice arthos four phosphate you can imagine that it would have four carbons okay now you think we're done but we're not okay we got one more thing that can

happen this arthros 4 phosphate I can do something else with it I can react it with another molecule that we might have just hanging around there there's another molecule hanging around and this one is called okay let's say you remember that ribulose 5 phosphate that ribulose 5 phosphate let's say I have another ribulose 5 phosphate over here and that ribulose 5 phosphate I have it acted on by a epimerase enzyme if it's acted on by an Epi merase enzyme what does it get converted into you guys know that it gets converted into specifically xylose five

phosphate okay well now what the body is going to do is it's going to take this xylos 5 phosphate and it's going to react with this arthos 4 phosphate now if these two react the zylos 5 phosphate and the arthos 4 phosphate are going to be acted on by another enzyme that enzyme is called a transketolase enzyme so I'm going to have another enzyme which is called trans ketolase enzyme and again it has thyine pyrro phosphate as a co-enzyme here and again it's transferring how many carbons it's transferring two carbons so it's a two carbon

transferring enzyme it's going to transfer two carbons from the xylos 5 phosphate onto the arthos 4 phosphate now if he's transferring two carbons then this five carbon will lose two carbons and turn into a three carbon molecule this three carbon molecule is called glycer alahh 3 phosphate not so bad and we already know where he can go we'll just draw a red line for right now showing it feeding over here into glycolysis but the two carbons that are transferred from this five carbon molecule are put onto this four carbon molecule and it leads to the

formation of fructose six phosphate and now we synthesize this fructose 6 phosphate and you guys already know where can this fructose 6 phosphate go he can also be fed into glycolysis okay this step here one 2 3 and four these four steps here are involved in a specific part of the the pentos phosphate pathway because it's actually divided into two parts what are the two parts here one is actually called the oxidative phase that's the four-step one okay this is the four steper the four step one that we went over and what is that including

again it includes glucose 6 phosphate going to glucose 6 phosphate dehydrogenate I'm sorry glucose 6 phosphate being acted on by glucose 6 phosphate dehydrogen to make six phosph glucono lacton six phosphoglucan lactone being acted on by lactonases to make six phosphogluconate six phosphogluconate act being acted on by six phosphor gluc glucon gluconate dehydrogenase which is also going to convert nadp positive to nadph and generating a CO2 to make ribulose 5 phosphate and then the conversion of ribulose 5 phosphate into ribos F phosphate and zylos phosphate that is the oxida phase the main purpose of the

oxida phase is two things one thing is to make nadph and the other thing is to make ribos F phosphate that is the purpose of the oxidated phase it's to make a lot of nadph and to make a lot of ribos FY phosphate now we'll talk about why that's important just a second but what's the other phase the other phase is actually called the non oxidated phase and I like to think about this one is just that carbon shuffling reactions carbon shuffling reactions in other words you see all these steps here afterwards after the fourth

step so in other words this step here we technically say the fifth step the sixth step the seventh step all those all these carbon shuffling where I'm going from ribos 5 phosphate and xylos 5 phosphate into glyceride 3 phosphate and cohose 7 phosphate these two reacting in forming fructose 6 phosphate and arthos 4 phosphate this guy reacting with the zylos 5 phosphate to make glycer 3 phosphate and fructose 6 phosphate those are my carbon shuffling reactions and what these are good for is that I didn't really show it here but look at this you see

this step here me going from ribos 5 phosphate to glycer 3 phosphate this is reversible this going from here reversible reversible reversible and this is also reversible and reversible what does that mean that means I can take things from glycolysis like what like the glyceride 3 phosphate and help to make ribos 5 phosphate so I can actually take glycer 3 phosphate fructose 6 phosphate and do what react these two together to get arthos 4 phosphate and xylos 5 phosphate which can actually be converted into ribos 5 phosphate eventually right then what happens happens then I

can take that arthros 4 phosphate act react with another glycolytic intermediate and make glyceride I3 phosphate and sedulo heptose if these two react I can get ribos phosphate and xylos phosphate so from the nonoxidative pathway what can I do I can make ribos I'm going to put r5p I just do it ribos five phosphate without making n adph and this can come from glycolytic intermediates so the whole significance of this pentos phosphate pathway is that I have two phases the oxidative phase which is generating a lot of nadph is and a lot of ribosy phosphate

and the non oxidative phase which is all those carbon shuffling reactions which the whole purposes is I can make ribos 5 phosphate without making nadph or and I can use gly itic intermediates or I can take ribos 5 phosphate and make glycolitic intermediates so in the reverse concept I could take ribos 5 phosphate I'm going put r5p and convert that into glyco litic intermediates so that is pretty cool okay so now that we understand this process here let me just mention here what is the significance of nadph what is the significance of ribos 5 phosphate

and the we're going to stop this video and do another video on the regulation okay let's take here and say nadph I already told you guys that nadph is very very good at being a good reducing agent he has reducing power they call it right so he's a good reducing agent he has reducing power for what type of reactions for any type of biosynthetic reaction what do I mean well if you guys have watched a lot of these metabolism videos you know that he's good for fatty acid synthesis we need him in a lot of

those fatty acid synthesis steps specifically the reduction steps if you guys watch the cholesterol metabolism video he's also important in cholesterol metabolism for being able to convert the HMG COA and the mevlani and he's also good for other different types of processes like one of them is specifically called nucleotide actually you need it for the nucleotide metabolism so synthesis of nucleotides and we didn't talk about it too much but it's also needed for neurotransmitter synthesis a lot of different things that this sucker can be used for so and we'll talk about a lot of these

things like the nucleotide synthesis and the neurotransmitter synthesis in individual systems and videos but just realize that this guy has a lot of uh significant things that he's involved in he's in significant for making fatty acids cholesterol nucleotides and neurotrans transmitters what about ribosy phosphate ribosy phosphate is equally as important and you'll see I should actually put one more thing in here if I can squeeze it in there let me actually just erase this a really really important thing that I did not mention it's also good for free radical reactions and we'll discuss that in

the next video really really important for free radical reactions it's acting as what's called an anti oxidant basically and you'll see exactly how it's helping it's not technically an antioxidant but it's helping antioxidant enzymes okay and the last one we said was ribos fi phosphate now ribos fi phosphate is important because he is involved in making a lot of different nucleotides like what you know he's important for making uh you know nucleotides are specific fre for nucleic acids because you know nucleotides are the basic building blocks for uh the nucleic acids like what like DNA

RNA oh it's also good for making ATP we actually use it as a building block for ATP we use it for those electron shuttles within the kreb cycle you guys have heard of them NAD positive and Fa D he's good for making these and he's also good for making co-enzyme a so he is very important in the synthesis of a lot of these different so I'm going to put here synthesis and then same thing so ATP synthesis NAD NAD positive synthesis fad synthesis co-enzyme a synthesis so he's very very important so you can imagine why

these things are so significant any type of alteration Within These could lead to disastrous effects specifically one that we'll talk about with respect to the free radical reactions is if there's a deficiency in a specific enzyme that generates these they can develop what's called a hemolytic anemia with Hines bodies so put hindes bodies for now okay but we'll talk about that in the next video okay so now we understand the the way that this pathway is occurring that the two phases oxidative phase which real quickly glucose 6 phosphate to six phosph gluconolactone six phosph gluconolactone

into six phosphogluconate six phosphogluconate into ribulose 5 phosphate and just the isomerization or epimerization to ribos F phosphate and xylos phosphate these are the oxida phases okay but the non oxidated phases is all these carbon shuffling reactions so when I take ribos F phosphate and xylos react them with the Trans ketolase react glyceride I3 phosphate culpas with a trans alalas and then reacting xilos five phosphate with the Ros four phosphate with the transketolase and making different glycolytic intermediates this is important for making ribosy phosphate without needing to make nadph or as well as taking ribosy

phosphate and make making specific glycolytic intermediates which also can be used in glucano Genesis and we'll talk about that in the next video all right guys I hope all this made sense I hope you guys did enjoy it if you did hit that like button subscribe please and please comment down in the comment section we look forward to hearing from you guys all right in the next video we'll go on to this in a little bit more detail all right engine nerds until next time