let's turn our attention to metabolic regulation. Now it turns out there's kind of a sweet spot in substrate. Concentration tends to be close to the K M of that substrates respective enzyme, and this essentially ensures that enzyme activity is going to noticeably fluctuate with changes, small changes, even in substrate concentration. So there's something called the elasticity coefficient, and this is basically just the slope of the line tangential to the Michaelis, uh, meant in curve. And you're basically at your most elastic slope, your greatest elasticity coefficient in this range of zero to U K M. So, you know, if you were to place a line tangent to this curve at, you know, some point, that's your elasticity coefficient at that particular point is the slope of this line. Uh, you don't really need to worry too much about the details. It's just the main concept that's important here. That's basically that yourselves. Wanna work with substrate concentrations that are going to cause noticeable fluctuations and enzyme activity, and the reason for this is regulation, right? So a deep and ATP, for example, their concentration doesn't fluctuate too much in the cell. A MP on the other hand amps. Concentration can fluctuate pretty drastically. Um, so a m p you know, for example, is going thio be, you know, the most one of the most important indicators of energy status in a cell, because its substrate concentration is going to have big fluctuation. Um, now and P activated protein kindness. Uh, that's going to basically be something that detects this change in a MP. Concentration actually is a really wide range of effects on metabolism. Um, you know, just one, for example, is, uh, you know it'll cause fatty acid oxidation in the heart and just interesting side note. The heart happens to be the only Oregon that can, uh, survive solely off fatty acid oxidation. Now, um, the enzymes that tend to be regulated are the enzymes that are not readily reversible, right? The readily reversible enzymes are generally not regulated because it's it's these enzymes that Dr Reactions right. These enzymes that are not readily reversible are the ones that really drive these metabolic pathways. So they're the more important points to regulate, because if you shut them off, you can shut off the whole pathway really easily. Right? So with that in mind, let's turn our attention. Thio like Allah assists and glue Konia Genesis to metabolic pathways that require very tight control. Because if you don't well, you can wind up with feudal cycles right where you just are expending energy and constantly, you know, mhm. Just taking the product of one reaction and flipping it back to the substrate and then flipping it back to the product. It just waste energy for the cell, right? You're spinning your wheels, so we want to avoid that. And the way we avoid that is by very tightly regulating these two cycles. So hex minus one, right? The first enzyme of black Hollis ISS is actually the most influential enzyme on the rate of Glen Collis ISS. But it's followed by Foster for two kindness, one which has, uh, you know, a noticeable impact on the rate of guy Kalle assist. But Hex Aquinas one has a really significant mhm influence. It's far and away the most influential enzyme on the rate of guy Kalle Assis, Um, and glucose six phosphate, the product of Hexham kindnesses. Reaction with glucose actually inhibits Hexcel kindness, right? So again, we're seeing that pattern where the product of a reaction serves as an inhibitor for the enzyme that carries out that reaction. Now there's another enzyme that we need to talk about. Uh, and that is glucose kindness, which also is known as Heck zucchinis form. It's an Isis. I am, uh, Isis. I'm form of Mexican and Ice One. Um, you know your book might use the term might prefer the term exogenous for just, um, used to calling it blue cockiness, Which is easier to say. So I'm gonna call it Blue kindness in these videos. But I'm always just talking about executing a sport. They're the same enzyme, so this enzyme is actually only present in liver cells, and it's stored in the nucleus of liver cells. And it's called out when it's needed. And what's cool about it is it has a much higher km, then hex kindness one right, so glucose causes glue kookiness. Glucose stimulates glue, cockiness to move from the nucleus to the cytoplasm. And once it's in the cytoplasm, Uh, Luca kindness is going to do the same thing that exogenous does right. It's going to add a phosphate group onto glucose to make glucose six phosphate. What's cool is glue kookiness is not inhibited by glucose six phosphate. So what's what's important about that is basically it means that in the liver cells anyways, right, this is only present in liver cells. So not in other parts of body but in liver cells. Uh, the supply of glucose is what determines the rate of production of glucose six phosphate, not the energy demand, not the demand for glucose, but rather the supply of glucose is used to gauge that reaction rate. So basically liver cells can continue to convert glucose to glucose six phosphate, even when they have crazy high amounts of glucose six phosphate. So hex, a kindness will shut down. Right? Uh, you know, if glucose six phosphate gets to be too high and concentration, it's gonna inhibit X skinnies, but not glucose Chinese. So glucose kind is gonna keep producing it. And this is important because the liver's main job in the body is like, really thio control. The glucose supply needs to make sure that it can deliver glucose thio all the cells of the body. So it's It's very important that there is this relationship in the liver where basically the production of glucose six phosphate is determined by the supply of glucose rather than demand for glucose like all the other cells of the body. So that's on. That's what this figure here is trying to show we have are just to be crystal clear. This is our reaction rate, right? A reaction velocity. And you can see that the K M of hex ickiness is way lower than that of glucose kindness. Right, Luca? Kindness can is like, I don't know, over here somewhere in Texas. Kinda like I can't even really draw it in that well, so cam of glue, kindnesses of way higher. That's what this figure is trying to show. So hex kindness is going to reach maximum velocity, much lower concentrations. Alright, let's flip the page.
