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Learn the toughest concepts covered in Biochemistry with step-by-step video tutorials and practice problems by world-class tutors

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


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because signals don't exist in a vacuum there coexisting within the cell. They interact with each other and they interact with each other and actually modify cellular response. And we call this phenomenon crosstalk like the signals are talking to one and thio one another. And you can see a simple example of that happening here with our all right insulin pathway and are epinephrine pathway. And you can see that there is going to be some cross talk right here. And you can, you know, this is very simplified image of it, and right next to it, you can see that it can get farm or complicated. Um, so here we're seeing the integration of many, many different signals all going on and again. This isn't even a complete picture. There's, you know, way more going on in the cell all the time. So hopefully this image kind of give you a sense of how complex and how interconnected these very signaling pathways are. Now there's another type of receptor we haven't talked about yet. And that is Guan. Well, cyclist receptors. So this is a receptor enzyme that's going to convert GTP to cyclic GMP. Sounds familiar. Yeah, because it's just like dental cyclists. Except now instead of ATP Teoh camp were doing GTP to cyclic GMP. And of course, this things happens in response to ligand binding. Now the difference here is with the den Lille cyclist that's actually activated. Bye protein G um which is turned on by ligand binding with these receptors Ligand binding actually activates. You know, the guano legal cyclist to convert GTP to cyclic GMP. So there's no protein g sort of intermediate going on in this interaction. Now, most of these receptors or membrane bound but there is one site is all like Guan a little cyclists that we know about and that is activated by nitric oxide. Just a little fact. Their cyclic GMP stimulates phosphate kindness. G cascade. It's now we're not just skipping, you know, a bunch of letters in the alphabet. It's foster kind. Um, I'm sorry I said foster kindness. I met protein kindness on its protein kindness G because it's activated by cyclic GMP. So that's where the G comes from. Interestingly, nitric oxide, the Ligon that activates the cycle site is Olic Guan. Well, cyclists, um is actually derived from Argentine and oxygen and it. Uh, nitric oxide actually causes a smooth muscle contraction. Now Viagra also has an effect on smooth muscle contraction. And that's because it actually inhibits cyclic GMP phosphate I astray. So remember, with cyclic a m p, we had that foster Dia Straits that breaks it down to help control the signaling pathway. So similarly, there's a foster disastrous that breaks down cyclic GMP to help control that signal toe. Help regulate that signal and so cyclic GMP stimulates smooth muscle contraction of the vein, leaving the Penis so Viagra inhibiting the phosphorus trays that breaks it down. I mean, it means there's gonna be, ah, lot of cyclic GMP present, meaning there's gonna be a lot of stimulation of the smooth muscle on that vein. Now, contracting the smooth muscle on the vein right is going to squeeze the vein, meaning it's going to limit blood flow out in a way towards the heart, meaning more blood is going to stay in that area and lead thio interaction. So that's how Viagra works. Kind of kind of interesting, right? Cem Riel world application of this stuff that we're talking about uhh asthma is, um, similar to, you know, what we are. We're just talking about there in that asthma is an immune response that causes smooth muscle contraction in bronchi A and, um, it, you know, unlike what Viagra does here with asthma, we actually use a beta adrianne ergic agonist that raises cyclic A M P levels and cyclic a m p does the opposite of cyclic GMP, right? So cyclic GMP stimulates smooth muscle contraction. But with asthma, you're too. You have too much smooth muscle contraction, making it hard to breathe. So by elevating cyclic A m p levels, we actually relax the smooth muscle and that opens up the airways and lets you breathe. So isn't that nice that zahau, like an asthma inhaler, works basically sort of like doing the opposite thing of what Bagger does now moving on. There are there's, you know, 11 are rather to more receptor types. We need thio mention, um, first amongst those is thes adhesion receptors called integrations, and they bind to the site a skeleton and collagen in the exercise cellular matrix. And basically, when these proteins change position, uh, the cells can change shape and form. So you know you have your site of skeleton here, and you have this integration, and it's gonna bind the site of skeleton and collagen in the extra cellular matrix. Here's our exceptionally matrix. This is site a skeleton. So you can kind of think of this is, um you know, like, a structural Uh huh. Receptor in a way. And again, when these move around, they can actually lead to the cell changing shape and form. Now, last type receptor we gotta mention are steroid hormone receptors. And unlike the receptors we've been talking about that are located on the membrane. Steroid hormone receptors are located inside the cell. And that's because, uh, steroids as a ligand, right? They can easily diffuse through the membrane. They don't need a transporter because they're readily lipid soluble. They actually need a transporter to move through the blood. And the site is all so anyhow, um, so steroids. This is, you know, a steroid hormone. So side note hormones can come in a variety of flavors, so to speak, there are steroid hormones. Previously, we were talking about, um, epinephrine, which is an amino acid derived hormone. Different type hormone, not steroid. Steroid hormones are have the backbone of sterile, basically and so sterile, Super lipid soluble. These guys, they're gonna defuse right through the membrane and inside the cell, they're going thio bind to the receptor and generally thes receptors will actually act as transcription factors. And you can see that happening here in this image where we have, um, the binding of steroid hormone two receptor. So what you see here and then that actually is gonna dime arise, enter the nucleus and, uh, you know, bind to the DNA and act as some sort of transcription factor for gene expression. However, some steroid hormones actually have their receptor inside the nucleus. Um so again depends on the hormone. However, they're usually going to be acting as transcription factors and affecting gene expression. All right, let's flip the page.