animals get a lot of credit for their ability to sense and respond thio things going on in their environments. But plants don't get the credit they deserve. So in this lesson, we're going to look at plants ability to sense and respond to what's going on in their environments. But before we get to the specifics of plants, I wanna talk generally about cell signaling. And if you want a bigger refresher than this, I recommend you go and check out our videos on cell signaling that will cover these ideas in greater detail. Now signal transaction, which is going thio. Results from molecular signals leading to some change in metabolism. Gene expression or something of like can be broken down into three steps. The first is reception. The signal is received, and this happens when a ligand, a signaling molecule, binds to a receptor and you can see we have to lie guns being released by ourselves. Here we have blue dot and red square, these air very important biological molecules. I'm kidding, by the way, so these Legans will bind to their appropriate receptors and notice how the receptors on these cells are the specific shape of these lions, right? This cell here has these receptors that will fit those red squares, and this one has receptors that will fit the blue dots. And guess what? That's because receptors and Legans are specific to each other, That is Liggins. Will Onley bind to specific receptors and receptors? Will Onley bind specific Legans? So our second step is trans deduction. The signal is carried through the cell and you can see that happening here These little molecules interacting with each other trying to represent here a cascade of molecular interactions that air carrying the signal from these receptors. Lastly, we have some response in the cell and this response is determined by the receptors present on the cell and the signal transaction pathways available to the cells. So you can see here that ourselves air kind of growing outward towards each other. That is their response from those molecular signals they received. Now there are many types of signaling molecules, but the one that I want to specifically are the type I want to specifically talk about is, or our hormones. Hormones are signaling molecules that will affect gene expression, cell division and growth. So these air super important signaling molecules, as we said about Legans, LaGon Zehr specific receptors, hormones or no exception there. Ah, hormone structure means that it will Onley bind to certain receptors that are meant to bind that hormone. So one way that a cell can mediate, or rather, one way that an organism can mediate its cells. Response is with the presence or absence of specific receptors for a hormone. For example, if I release blue dot hormone and some of my cells don't have any receptors for the blue dot hormone, then they won't receive the signal. So by including or not, including the necessary receptor, you can mediate whether or not a cell will respond to that signal. Now another really cool thing about hormones is their ability to our the ability of their signals to be amplified. So signal amplification will result when ah, few signaling molecules have a huge effect. So in our little diagram, we have our hormone here, and this hormone will influence this protein too, you know, do something to this molecule, and this molecule will have an effect on two molecules, and each of those blue molecules will have an effect on two pink molecules and so on and so forth. So this is a huge oversimplification. But hopefully you get the general idea that a single hormone can lead to on effect on many molecules downstream. That's what we mean by signal amplification that you can amplify the signal as you carry it. Now, often the a signal trans duck shin pathways will involve what are called phosphor relation cascades, which is when you basically have a Siris of proteins that activate and deactivate each other through the transfer of phosphate groups. And you can see sort of, ah, model of what that might look like here, where you know, the ligand binding at this receptor leads to the activation of this protein. And that protein activates this protein, and that protein activates this protein and so on and so forth. And you have a cascade of activation and deactivation and the whole time they're transferring phosphate groups to essentially turn each other on and off. Now, you can also have what are called second messengers, and these are intracellular signaling molecules. So they signal within the cell and they're gonna be involved in various signal transaction pathways. We have a little model for one. Right here. Uh, this is the, you know, a new interest cellular signal being carried through these various molecules. So this would be our second messenger. And that's going to activate a syriza signaling molecules and elicit some response in cell. Let's turn the page.