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Video transcript

in this video we're going to talk a little bit about membrane receptors membrane receptors are really important because they are the things that actually allow our cells to communicate with the outside world without membrane receptors our cells wouldn't be able to work together and they wouldn't be able to form the human body as we know it and so membrane receptor is essentially an integral protein that is embedded in the cell membrane that takes part in communication with the outside environment and so for short I'm just going to say it's integral protein that communicates with the outside environment and so the way membrane receptors work is that in our bodies they're a bunch of these signaling molecules going around we call these extracellular signaling molecules because they are outside ourselves let's say this outside area is the extracellular portion let's say we have a pink signaling molecule for the sake of diagram I'm going to say it looks like a triangle now in reality of course signaling molecules do not look like triangles signaling molecules can be a variety of things they can be ions or molecules essentially that bind to another chemical entity we also call these ligands and a lichen can be something like a neurotransmitter or hormone cell recognition molecules and what these can do is these can attach to our membrane receptors and trigger jane jizz inside the cell I'm going to do the membrane receptors in a nice blue color and remember we say they're integral proteins and integral Bodines are proteins that go through the entire cell membrane so let's say here we have our nice integral protein and so what will happen essentially is this ligand will bind to our integral protein and so this and this integral protein which again appears in our cell membrane will actually bind to that nice triangle-shaped ligand that we have like this and so now what we have is our ligand receptor complex just a fancy way of saying our liking on our membrane receptor have bound and once this happens this can essentially tell the cell what to do this can explain things like how hormones function how our nerve impulses work why our cells divide cell death it also explains why our cell allows certain things into the cell and other things not sometimes in terms of a bigger real-world application this is really critically important in designing pharmaceutical drugs in fact a very big percentage of pharmaceutical drugs actually target our membrane receptors this is actually why some drugs can target specific cells like some drugs might only target your liver while other drugs might target your heart and the reason why is because different cells might actually have different receptors and these receptors might bind different things this whole process of binding and telling the cell what to do we actually have a really special name for and that's called signal transduction so this is a process that we call signal transduction what happens during signal transduction is an extracellular signal molecule so this is our ligand binds to our membrane receptor and these receptor proteins then cause an intracellular response and so what after binding there will be what's called an intracellular response and so this receptor will bind to the protein and this will cause the protein to actually change conformation which then activates intracellular signaling proteins so proteins on the intracellular side of the cell and this activates a cascade of protein signals that will alter the behavior of our cell sounds really complicated essentially the way this works is we have an original signal our ligand this can be again a hormone and you're a transmitter something like that and this original signal is passed along it'll bind to our protein and that protein will tell other proteins and inside the cell about what's going on and this signal is propagated throughout the cell causing the cell to perform a specific function now you'll notice that in the diagram we actually drew a really specific shape for our ligand we chose a triangle now I chose a triangle be a little easier to draw but this triangle actually fits right into the protein that I was drawing which has like an empty triangle space this is actually really important each specific receptor so the thing that's missing a triangle can only bind to a few types and often only one specific type of ligand so it can only bind that specific triangle pink likened membrane receptors allow our body and cells to transfer information and it can be very very specific about it this is important because when our body releases a hormone it's kind of floating around in our entire bloodstream how does our pancreas know that the hormone is intended for for it how would our heart cells not react to it and this is why the membrane receptors have a very specific preference for certain specific types of ligands this is what we call our lock and key model so if we imagine our ligand as the key and our receptor protein has a lock our receptor protein as a lock needs a very specific type of key in order to open it so just like how our key chain we might have a key to our mailbox in a key to our front door maybe a key to our desk each of these keys does something different and opens a different lock that's kind of hiked our cells work now I just want to make a note that this is a slightly outdated model and our updated model is actually what we call induced fit and these two concepts are very similar but instead of saying that the ligands and the membrane receptors have a very very specific shape induce fit brings a little more flexibility and it says the ligands and the membrane receptors can sometimes change confirmations kind of like how dough can be a little squishy so that they can fit each other now overall there are still ton of new membrane receptors that are being discovered as far as we know we can group memory receptors into three large groups the first group we call ligand gated ion channels the second group we call g-protein coupled receptors and lastly our third group we call enzyme-linked receptors now in summary essentially we have really important membrane receptors in our cell membrane and these are integral proteins that allow our cells to communicate with the outside environment and the process in which these integral proteins work these membrane receptors work is that we have a ligand which can be an ion or a molecule it can bind to our integral protein causing a process that we call signal transduction and signal transduction essentially means that our original signal or lichened is propagated throughout the cell as Co different proteins are activated causing our interests early response ligands and memory receptors have a very specific fit only specific ligands can bind with specific membrane receptors we call this lock and key a more updated name for it is induced fit in which the ligands and membrane receptors are a little more flexible kind of like dough they'll actually slightly alter confirmations when they fit together and all of these membrane receptors that we know so far can be grouped into three major groups ligand gated ion channels g-protein coupled receptors and enzyme-linked receptors