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Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway

Pentose Phosphate Pathway


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the pen toes Phosphate pathway is a very important pathway for generating crucial materials for the cell. Now it's often confused by students because it is not a linear pathway like we're used to seeing right. We don't have one set starting material and wind up with one set product. The pen toes, faucet pathways, more like a Web. We can put certain things in and get certain things out, and there's actually a number of different useful products that the pantos phosphate pathway yields. Um, generally speaking, though, uh, the pen toes phosphate pathway will take glucose six phosphate as it's starting material and in in sort of one of its simplest paths, or one of the most basic paths that you can travel through it. It will take that glucose six phosphate make to N A. D. P. H. And a wry Bulus. Five. Phosphate now ride Bulus five. Phosphate is super important for producing ribose five phosphate, which is a molecule used for nucleotide synthesis and also history and synthesis so that h there. That's history in the amino acid now, uh, also is important for producing a re throws for phosphate, which is a molecule that's used to make the aromatic amino acids phenylalanine, tryptophan and tyrosine. What's also interesting about the Pento sauce fate pathway is it's capable of completely oxidizing glucose. Now, you might remember like Hollis is actually can't do this like Hollis ISS will partially oxidized glucose, but it won't fully oxidize it. Uh, that, uh, that will happen to the Piru baits that are generated from Glen Collis ISS during the course of the citric acid cycle. But, like Hollis is alone won't fully oxidized glucose. However, the pantos phosphate pathway can fully oxidized glucose. Now you also produce N a d p h from the pantos phosphate pathway, and this uses N a D p plus instead of N a d plus. So N a. D. PH is very similar to N a. D H. It's kind of like a nana log of it. The difference in terms of molecular structure is the presence of a phosphate group. That's what the P ISS for. There's a phosphate in N a. D. PH. That is not in any D. H. Um, but the molecules are very functionally similar. However, any DPH does not play a role in oxidative phosphor relation, like n a d h does n a d pH. Well, I shouldn't say that any DPH doesn't play a direct role in oxidative phosphor relation. Uh, like n a D h does. Because, you know, in a d H, which brings electrons to the electron transport change and a d. PH doesn't do that. It does, however, sort of play a support role. We're going to talk about that. The bottom of the page plays a support role in terms of preventing oxygen toxicity so more on that later. But first, let's take a look at sort of the basic path you can trace through the Pintos phosphate pathway. So looking here have four reactions listed, actually only showing the first three of those reactions. So this is reaction one, two and three. Uh, and the first reaction is carried out by glucose six phosphate di hydrogen. A. So it's a D hydrogen is we're going thio. Get rid of the water and that takes glucose six phosphate and it turns it into six fast for Luke. Oh, no black tone. I know there's a delta in the name. It's too much to write out, uh, in the process we generate an n a D. PH. Next reaction is carried out by lack tennis, as the name sort of implies, this is going to break the lack tone ring, and it's going to generate six Foss foe glue. Oops, gluconate. Now, the last reaction we're seeing here is carried out by six phosphate blue di hydrogen. It's against the D hydrogen iss. So we're going to you. Ah, dehydrate. Dehydrate rather are molecule and uhh this is going to generate. Let me jump out of the image here, Reid. You loose five phosphate. So uhh! In the process of doing that, of course, we also produce an n a d pH. That's where our two n a d. PH has come from Now, once we've made Regulus five phosphate, we we can use phosphate pantos I som race to actually turn it into ribose five phosphate. We're going to see that in the image below. Lower on the page. Um, this is a reaction against carried out by a nice samba race, meaning it's going to have a Delta G very close to zero. So it's very easily reversible. It's nice. I'm race. We're just doing a little rearrangement of the molecule. And if we do that, then that ribose five are ribose. Five phosphate can be used for nucleotide synthesis. Now we actually can make a variety of sugars from rival US five phosphate and they have different uses, different functions. And before we get into this part of the pathway, I just want to quickly mention the enzymes we're gonna be seeing, which are trans key laces and trans all places. Now trans key laces are going to the enzymes that transfer to carbon units. So two carbons stuck together moved over to a different molecule. Trans Aldo laces are going to transfer three carbon units. And it's worth noting that trans key laces air going to use this molecule timing pyre phosphate as their transfer agent. Alright, so let's take a look at the figure here. No notice. We're starting with Rival owes five phosphate. And I know this figure. All the images se Fosse fat. That's because it's actually uh, not a figure from an English source. It's actually from a Dutch source, I believe so. I know it's Foss fat instead of phosphate. Doesn't matter. Same molecules were just dropping the e. And if you want to pronounce it correctly put on little Dutch accent. Anyways, we start out with Rival Owes five phosphate, which is a five carbon molecule. And from there, like we said before, we can use that I som race to make ribose five phosphate or we can actually also I summarize it into Zedillo's five phosphate, and both of these are five carbon sugars. Now, here's where this part of the pathway gets a little more confusing. You actually need both of these. You need the ribose five phosphate and the silos five phosphate to carry out this next step that we're seeing here represented by these curvy arrows. So you need both of these molecules. Meaning you needed, uh, to Regulus. Five phosphates being rearranged, one into ribose, five phosphate, one in desire list, five phosphate. And then you're going to use a trans key delay. So this is a trans heat, a lace reaction, and we're going to take, um, we're going to take to carbon units from Silas five phosphate. Transfer it to ribose five phosphate, and then we're going to end up with the rivals. Five phosphate is going to become, uh, Cito Hep Telos seven phosphate, which you don't need to know the structure of you just need to know it's a seven carbon molecule, and Silas by phosphate is going to be left left as G three p again, this is the Dutch name. That's why it looks a little funny, but this molecule is G three p or glycerol to hide pretty phosphate. Um, from here we can use a trans Al Dallas, and it's worth. It's worth noting g three p. That's a molecule that could be fed into other metabolic pathways. Right? That is a very useful molecule. Uh, but we can take these two molecules and use a trans al delays and transfer three carbon units from Cedo hep Telos to G three p. So doing that will produce a re thrace four phosphate, which is a four carbon molecule. Right. We had seven carbons transferred three, so we only have four left. And, of course, this molecule can be used to synthesize are aromatic amino acids. Or, uh, I'm sorry and rather not or and will produce a fructose six phosphate, which is a six carbon sugar. And we've seen this molecule come up before too. It can be fed into theme the metabolic pathways we've been talking about. Um, so yeah, you know, you can It doesn't have to end here. You can continue to transfer carbons around. The next part of the image is showing, um, showing, you know, various various other carbon transfers. Um, however, we're going to stop our discussion right there, because all you really need to take away from this is the action of trans key laces and trans Alva laces and how to produce, uh, Cedo Heptulla seven phosphate G three peat free throws for phosphate and fructose six phosphate. All right, now, before we turn the page, let's get back to any DPH and talk a little bit about what it does. So any DPH is a, uh is a molecule very similar to an a D. H. Meaning it will very easily reduce and oxidize. Um, unlike N a d h, though it's not going to donate its electrons to electron transport. Instead, it's going to use them to help prevent oxygen toxicity from super oxide radicals. Which are these molecules right here? 02 minus. That is a super oxide radical. Uh, so what's gonna happen is super oxide dis mu taste is going to take those super oxide radicals and convert them to hydrogen peroxide. And if you're thinking wait, isn't hydrogen peroxide uh, you know, uh, very or not very but a dangerous agent. Uh, a dangerous oxidizing agent you have around your cell. Well, absolutely. Yes, it iss um However, however, the cell would rather have hydrogen peroxide than those super oxide radicals, it's less dangerous with hydrogen peroxide. Uh, your cells will use this enzyme glutathione, reductase, peroxide, ace. And basically it's going thio oxidized, glutathione, and it's going thio convert hydrogen peroxide into water. Right and water is not dangerous. So this is going Thio this is going to make our going to take that hydrogen peroxide and make it no longer harmful. And in the process, we are going thio oxidize our Bluetooth. I own so glutathione reductase is going to use our n a D. PH. Now we're getting back to any day pH glutathione reductase uses n a. D ph to convert Bluetooth. I own back Thio. It's active form, right? It got oxidized when we turned hydrogen peroxide in the water. So we need to reduce it. Um and we're going to reduce it with glutathione reductase and in a d. PH. So in a d. Ph is going to provide the electrons for the reduction of glutathione to get it back into its active form. Uh, it's also worth noting that any DPH inhibits glucose is entry into the penthouse phosphate pathway via feedback inhibition. So if we are over producing on our pantos phosphate pathway, we're gonna have too much and a d pH and that's going thio feedback and actually inhibit the pantos phosphate path or inhibit glucose is entry into the penthouse phosphate pathway because we don't need to produce any more than 80 ph. All right, let's turn the page.