Introduction to Biosignaling

in this video, we're going to begin our introduction to bio signaling. And so bio signaling, you can see has the root word bio in it, which, of course, we know means life. And so bio signaling is really just the signaling of life. And so it's really defined as the ability for all living cells to produce, receive and respond to external signals and conditions. Now, bio signaling really allows cells to respond to stimuli, and it also allows for effective cellular communication between cells. And so, if we take a look at our image down below right here, you can see we have a little representation toe help. You guys better understand bio signaling. And so over here, what we have is our cell. And this cell, which will notice, is our signaling cell. And so are signaling cell really acts almost like an archer, which has, ah, bow and arrow pointed at another cell. And so the signaling cell is going to produce some kind of signal or some kind of lie again, such as this molecule that we see right here and that lie again has the ability to diffuse to different areas. And so this lie again will make its way over to another cell over here. And this cell is going to have the appropriate receptor in its plasma membrane that will bind the Lagan. And so this cell over here is referred to as the target cell because it has the specific receptor for this specific LaGon that was released. And so you can see we have the little targets them over here to remind you guys of that. And so you can see that the ligand binding to the receptor is going to cause a cascade of interest cellular events within the target cell that ultimately leads to a cellular response. And so this, you can see, is a form of cell communication because we have one cell over here producing a signal and causing a cellular response within a different target cell. And we'll be able to see examples of bio signaling as we move forward in our course. Now, over here on the right hand side, what we have is just a small list of some examples of different types of bio signaling molecules. And so these Liggins, these bio signaling molecules here could be antigens, growth factors, hormones light mechanical touch neurotransmitters and much, much mawr. Again, this is just a small list, and moving forward in our course will be able to see different examples of different types of bio signaling molecules. But for now, this year concludes our introduction to bio signaling, and in our next lesson video, we'll talk about signal Trans duck shin, so I'll see you guys there.

in this video, we're going to introduce signal trans Duck shin now signal transducer Ction is really just a cell process that, as its name implies, trans deuces or converts, extra cellular signals or extra cellular information into an intracellular chemical change or an intracellular response. And so really signal Trans Duck Shin requires a minimum off at least two key components, which will talk about down below now. Normally, signal transaction includes mawr than just these two key components, but here we're just introducing the bare minimum key components that would be required for signal transaction. And so this first key component is going to be a ligand. And, of course, we've covered in our previous lesson videos. What a lie again is so we already know that a lie again is a small molecule that specifically binds and forms a complex with another bio molecule. And in this context of signal transaction and bio signaling, this bio molecule is going to be a receptor protein, and really that leads us to our second key component, which is going to be the receptor. And again, this receptor is typically going to be an integral membrane protein that's embedded within the cells plasma membrane and this receptor protein is going to undergo a change, a confirmation, all change upon ligand binding. And so this lie again is going to bind to the receptor and then the receptor is going to undergo a confirmation. I'll change, and at that point after the confirmation, I'll change. That opens up Ah, lot of different possibilities for the continuation of signal trans duck shin. And so, if you take a look at our image down below, over here on the left hand side, you can get a better idea of signal trans duck shin. And so notice that add the top here. This blue molecule represents our ligand or our primary messenger. Since this is really the first molecule that's going to elicit the signal transaction pathway. And so this like and of course, is going to bind very, very specifically and form a complex with this receptor that we have down below. And again, the receptor is typically going to be an integral membrane protein that is embedded within the cells plasma membrane, as you see here. And of course, once the lie again binds the receptor, the receptor is going to undergo a confirmation. Allchin change and again, once the receptor undergoes a confirmation will change. That opens up ah lot of different subsequent possibilities here. What we're showing is that the confirmation I'll change leads to the activation of a defector enzyme. And then this effect, er enzyme produces a secondary messenger that diffuses into the cytoplasm and ultimately leads to the cell response. The generation of a cell response. And so really, all of the events that we see taking place right here would be an example of signal trans duck shin. Because again, signal transaction is when the cell trans deuces or converts extra cellular signals like the Ligon or the Primary Messenger and converts this extra cellular signal into a chemical change or a chemical response. Ultimately, a cell response. And this is the process that would lead to that cell response. And so that is what's referred to a signal transaction now moving forward in our course will be able to talk about lots of different examples and specific examples of signal trans duck shin. Now, it's also really, really important to note here is that the receptor ligand interactions or the interactions between this like and and this receptor right here are actually protein ligand interactions. And you might recall that way back in our previous lesson videos, we actually covered protein ligand interactions in a lot of detail. And so because receptor ligand interactions are protein ligand interactions, everything that we talked about in protein, leg and interactions also applies to receptor ligand interactions. And so if you don't remember anything about protein ligand interactions, please be sure to go check out those old or lessen videos because again, all of the information in the protein ligand interactions videos also applies here two receptor like in interactions. And so if we take a look at our image over here on the right hand side, these images should look familiar to you guys somewhat familiar to you guys from our protein ligand interaction videos and so notice here. What we have is our free receptor symbolized by our and over here what we have is our free ligand symbolized by l and of course, the receptor and lie again combined to each other to form a receptor ligand complex R l and notice that this is a reversible reaction which means that it can proceed in the four direction, but it can also proceed in the reverse direction. And it's possible for the receptor and the like and to disassociate from each other. And so notice down below. Because again, this is a reversible reaction. That means that the dissociation equilibrium, constant K d. Also applies here. And so recall that the K D is just the equilibrium constant for the dissociation of the receptor, like in Complex and because it's the equilibrium constant we know is that it's gonna be the concentration of the product of the products over the concentration of the reactant. And so, for the reverse reaction here, the products are going to be the free receptor and the free Ligon. And of course, of course, for this reverse reaction, the reactant is going to be the receptor like in complex. And so that's why it's in this format. And again, these are all older concepts that we talked about in our previous lesson video. So if this looks completely foreign to you guys, please make sure to go back and check out those older lesson videos. And so this year concludes, our introduction to signal transaction and moving forward will be able to get a little bit of practice applying these concepts, and I'll see you guys in our next video.

A sample of cells has a total receptor concentration of 10 mM and a free ligand concentration of 15 mM. If 25% of the receptors are occupied with ligand under these conditions, calculate the receptor-ligand dissociation constant (K_d).

• A. 7 mM.
• B. 38 mM.
• C. 12 mM.
• D. 45 mM.

Which hormone from the plot below shows the highest binding affinity for the receptor?

• A. Hormone X.
• B. Hormone Y.
• C. Hormone Z.

so moving forward in our course, we're going to talk about ah, lot of different bio signaling transaction systems. But before we move forward in our course and talk about the details of all of those bio signaling transaction systems, it's important to take a step back and look at the common features that all of these bio signaling transaction systems share. And so here in this video, we're going to talk about the five features that pretty much all bio signaling transaction systems share and so you can see that we have each of these five features number down below in our table and over here on the right, what we have is images to portray each of those features. Now the very first feature here is specificity, which is really exactly what it sounds like. And it's referring to this idea that receptor lie again. Interactions are super super specific, and so what this means is that receptors will not just respond to any like, and they will Onley, bind and respond two very specific, like ants. And so over here in this image, you can see that we have our receptor and noticed that the circular green like and here is perfectly shaped and fit for this receptor and notice that this red square shaped like in over here is not fit for this receptor. And so the receptor will not respond to this leg in, however, it will respond to the circular green light again. And so that's exactly what this idea is referring to. That the receptor ligand interactions are super super specific to each other. And so moving onto the second feature here, what we have is amplification, which is also exactly what it sounds like. That signals will get amplified. And so this is the idea that even if you have just one single receptor ligand interaction, ultimately that one single receptor like in interaction will lead to many downstream interactions. And so, over here on the right hand side, you can see the portrayal of this particular feature of amplification and so notice. Here we have our lie again binding to the receptor, and that represents represents our single receptor like in interaction. But ultimately we know that it's going to lead to many, many downstream interactions, and so you can see that ultimately it could lead toe one molecule getting activated which would activate two molecules. And then each of those would activate to mawr. And ultimately what happens is you get many, many molecules that are affected through the, uh, interaction of just one single receptor, like in interaction. And so that shows the amplification of the single signal. Now our third feature here, that pretty much all bio signaling transaction system share is modularity, and this is the idea that a system's components are modular and they can be modulated, or they can be modified in order to elicit many different responses, and they could be modified for many different uses. And so, over here on the right, we can see a portrayal of that idea and so notice that we have our single receptor like an interaction. But the bio signaling transaction system could entail modifications, and so there's one pathway that could lead to an active ends on which would lead to sell response number one. But then, of course, the same exact receptor, like an interaction, could be modified so that its signal transaction leads to the inactivation of an enzyme, perhaps through phosphor relation, like as we're showing here, and that an activation of the enzyme could lead to sell response number two. And so ultimately, what we're seeing here is that a bio signaling transact production system can be modulated for many uses to elicit different cell responses. So now moving on to feature number four, it is adaptation. And of course, this is exactly what it sounds like. That a bio signaling transaction system can actually adapt to several different scenarios. And it can do this through positive and negative feedback regulation. And so if we take a look at this image over here, notice we're showing you again. Our risks are ligand receptor interaction right here. And notice that this signal transaction system leads to the activation of all these different enzymes which ultimately leads to product f over here. But if product F is getting over produced product, F can actually come back and inhibit this receptor ligand interaction so that it can help decrease the production of F. And so this is a way for the system to adapt to the scenario where F is over produced and this is showing a an example of negative feedback regulation, since it's inhibiting this receptor like an interaction. But this could also occur through positive feedback regulation as well. And so it is possible for a system to adapt to different scenarios. And so our fifth and final feature that all bio signaling transaction system share is integration. And of course, this is the idea that a system can actually integrate, uh, with other systems, and so it can therefore produce a unified and scaled cellular response, especially if these two systems are producing opposite cell response effects. And so notice over here in this image we have two different bio signaling transaction systems. We have this purple and green receptor ligand interaction, and then we have this blue and red receptor like an interaction. And so notice that these two bio signaling systems can be integrated in order to create a unified and scaled, appropriately scaled cell response. And we'll be able to see ideas of integration as we move forward in our course as well. And so really, this year concludes our lesson on the five features of bio signaling transaction systems, and we'll be able to see examples of all of these five features as we move forward in our course and talk about specific bio signaling transaction systems. And so that concludes this video, and I'll see you guys in our next one

Which of the following statements regarding signal transduction pathways in cells is FALSE?

• A. A ligand, such as a hormone, binds to a specific cell surface receptor on a target cell.
• B. Signal transduction cascades, often involving protein kinases, amplify a signal intracellularly.
• C. A receptor changes conformation upon ligand binding, transmitting a signal across the cell membrane.
• D. Signal transduction cascades directly transmit a single stimulus to one, single target, identically in all cells.
• E. Phosphatases remove phosphoryl groups from polypeptides, regulating a cell's response.

So as we move forward in our course and talk about different types of bio signaling pathways, what we're going to see is that these enzymes, called kindness, is actually play a large role in bio signaling and these kindness enzymes they helped to create the cell response that's associated with bio signaling now moving forward. In our course, we're going to see different types of kindnesses. And so, really, that's the main focus of this video. Now. Also recall that way back in some of our previous lesson videos, when we talked about different types of enzymes that we already covered kindnesses. And so we already have an idea that kindnesses are just enzymes that Foss for late or add phosphate groups to their substrates. And they do this by utilizing or hide relies ing a t p. Now, when kindnesses Foss for late there substrates with themselves, it's actually a really big deal. And the reason that it's such a big deal is because the phosphor elation of target proteins actually leads to altered activity of the target protein. And so, by alteration of activity, what we really mean is that it could lead to either the activation of that target protein, or it could lead to the inhibition of that target protein. But really, there's no solid way to predict whether phosphor relation is going to activate or inhibit a particular target protein. It's going to be different on a case by case basis, and so you should never assume that foster relation will lead to activation. And you should never assume that foster relation would lead to inhibition again. It will be different on a case by case basis. Instead, what you should assume is that phosphor relation will lead toa altered activity of that target. Now again, as we move forward in our course, we're going to see different types of kindnesses. And so really, two of the most common classes of kindnesses are the searing three inning kindnesses, and the tyrosine kindness is now. The Syrian three inning kindnesses, as their name implies, are kindnesses that foss for late, either searing and or three inning residues on their target proteins. And so it turns out that Syrian three Indian kindness is actually make up about 25% or 1/4 off all kindnesses, which is actually a pretty large percentage if one out of four of all kindnesses are going to be Syrian. Three inning kindnesses and so Syrian three inning kindnesses is definitely a class of kindness that you guys should be familiar with moving forward in our course now the second again. The second common class of kindness are the tyrosine, kindnesses and as their name implies, these air kindnesses that Foss for late the amino acid residue tyrosine on their targets. And so notice that down below, over here on the left hand side, what we're showing you are the Syrian three and in kindness is. And then over here in the image on the right hand side, we're showing you the tyrosine kindnesses and so focusing on the Syrian three inning kindnesses again, they will either fast for late the amino acid residue Syrian or three inning. And so, of course, it's going to utilize a Syrian three Indian kindness. And so these Syrian 39 kindnesses will utilize a teepee and hydrolyzed 80 p toe a d p. And in the process they take that phosphate group and they added on to their targets at these particular residues, either Syrian or threatening to create phosphorus, Syrian or phosphate three inning. And again, this is a big deal because the phosphor relation of these residues is going to lead to altered activity of that target. Now again, over here on the right, what we're showing you is the tyrosine kindness and, of course, tyrosine. Kindnesses are going to foster for late the amino acid residue tyrosine on their target proteins. And in the process, they utilizing hydrolyzed 80 PTO ADP while adding a phosphate group to the tyrosine residue. And so we could go ahead and inter actively fill in our phosphate group here so it would look like this and we can add in our negative charges. And so this year represents the phosphate group, and this is fossil attire scene and again, this is a big deal. The phosphor relation of this residue could be a big deal, because it's going to alter the activity of that target protein and again as we move forward in our course, we're going to see Syrian three and in kindness is and we'll see tyrosine kindnesses. So keep these in mind as we move forward in our course. But for now, this year concludes, our introduction to the types of kindness is, and I'll see you guys in our next video

Why is the activation of a protein kinase an important step in signal transduction?

• A. Kinases bind to receptors and prevent binding of the ligand.
• B. Kinases prevent signal amplification by degrading specific enzymes in the cell.
• C. Kinases can activate or inactivate proteins by phosphorylation.
• D. Kinases are secreted by a cell as a signaling molecule.

So again, as we move forward in our course beyond this point, we're going to talk about ah lot of different types of bio signaling pathways. And what will realize is that these different bio signaling pathways utilize different types of bio signaling receptors. And so, really, that's the main focus of this video. Thio Introduce these different types of bio signaling receptors. So really, there are two major types of integral membrane protein receptors that you guys should know that are involved in most signal transaction pathways. So the first major type is the G protein coupled receptors or the GPC, our first short. And so here in this blank we can fill in GPC are, and the second major types are the receptor tyrosine, kindnesses or the R T K for short. So over here we can fill in rtk now again as we move forward. In our course, we'll see specific examples of G couple protein receptors or GPC arse, and we'll see specific examples of receptor tyrosine, kindnesses or RT case. But for now, we're just introducing these receptors Now. What's important to note is that the G. P. C. R s and the RT case will actually transducer extra cellular signals via fundamentally different mechanisms. And again, that's why we're going to cover each of these types of receptors separately in their own individual videos as we move forward in our course and so down below in our example, notice that we're going to, uh, introduce the G, p, c R and the R T K. And so the image over here on the left is showing. The GPC are signaling and so notice that we have the like end up above and the GPC are is this protein that we see embedded within the membrane and later in our course will see that this GPC our associates with what's known as a g protein. But again, don't worry too much about this now because we're going to talk about this in more detail later in our course For now, what you could do is just get annoyed idea of how we're going to portray the GPC are moving forward in our course and then over here on the right, what we're showing you is the rt k bio signaling receptor. And so again, the Legans are up above and you can see that the receptor here for the R T. K s actually has these two different monomer units. And again, don't focus too much on the details here because we're going to revisit our T. K s later in our course. Really, The major take away is that we're gonna be talking about two major types of bio signaling receptors the G p C. R s and the RT case. And this is kind of what they're going to look like moving forward. And this is what the Arctic's is gonna look like moving forward. And so this here concludes our introduction to the two types of bio signaling receptors GPC arson R T case, and I'll see you guys in our next video.

in this video, we're going to introduce our map of the lesson on bio signaling pathways, which is down below right here. Now, as we move forward in our course and talk about different bio signaling pathways, what we'll see is that these bio signaling pathways can really be grouped into three different categories that we have color coded here by their backgrounds. And so we have this green background over here on the far left and thes air bio signaling pathways that utilize G protein coupled receptors or G p. C. R. S. Then notice over here in the middle with the pink background. We have bio signaling pathways that utilized receptor, tyrosine, kindnesses or arty case. And then over here on the far right, what we have is bio signaling pathways that utilize lipid hormones. And so again, as we move forward in our course, we'll talk about bio signaling pathways that are in each of these groups. Now, just like the maps that we saw in some of our previous lesson videos, this map was specifically constructed so that it is a reflection of our lesson on bio signaling. And so what that means is that we're going to explore this map in a similar way that we explored the maps in our previous lesson videos. And so we're gonna explore the left branches first, and we're going to continue to explore left branches until we've explored all of the left branches. And then we'll start to zoom out and explore the right branches. And then once we've explored all the branches in that pathway, we'll go ahead and move on to our new branch again, exploring to the left first and the same fashion that we did in our previous lesson videos. Now, one thing to note that's different about this map is that we've intentionally left thes interactive blanks here throughout the map. And so we've done that because when we move through the course, we're going to revisit this map and fill in these interactive blinks. And so you can expect to revisit this map of the lesson on bio signaling pathways several times as we move forward in our course, and so again, we're going to start by exploring the left most branches. So in our next lesson video, you should expect to cover G protein coupled receptors or GP CRS, and that's exactly what we're going to do. So I'll see you guys in our next video