Ligand Gated Ion Channels
Learn about how ligand gated ion channels work in the cell membrane. Created by William Tsai.
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- At minute3:00specifically, (2:47to3:01) it seems a bit unclear why ligands bind at a place distant from the actual channel. Why is so?(4 votes)
- The idea is that a ligand binding isn't like wedging a door open with a door stop. It's more like opening an elevator door with your finger: your finger is the necessary ligand but it's not physically forcing the door open as the wedge would. Rather, the entire "conformation" of the elevator door (gears, belts, etc) changes because of your finger.(27 votes)
- Stretch-activated channels being the same as stress-gated channels, I assume?(8 votes)
- You can find more information about stress-gated channels when you look-up mechanosensitive channels. "Stress" and "stretch" are ways to describe the tension that is acting on the plasma membrane. Lipids near the mechanosensitive channels transfer a tension force that causes the channels to open/close.(1 vote)
- This video way to cofusing , why mention all those other channels voltage ect not to be confused with other channels . the video was talking about Ligated stick with that subject and make a video of the others(0 votes)
- I completely understand your frustration, my professor practically rushed through this chapter and its highly difficult to actually sit there and try to understand the differences between the following channels. I think he just said that so in the near future if you were to see voltage channel you already have an idea that it is not the same as a ligand ion channel(27 votes)
- What do the ions that were listed in the video end up doing inside the cell?(3 votes)
- It depends. In the case of neurons, ions entering a cell could cause or increase the likelihood of an action potential. The ligand could be a neurotransmitter that increases the sensitivity of the neuron to a stimulus. For instance some drugs change your sensitivity to pain based on specificity to certain neurons and their ability to alter the electrical potential of your cells.(6 votes)
- Do all the channels open by one ligand attachment or are there equal amounts of Ligands to channels?(3 votes)
- https://en.wikipedia.org/wiki/GABAA_receptor Don't understand- here GABA (ligand) is binding to ACTIVE SITE of this ligand gated ion channel....explain? Misleading maybe that this video says these ligands just bind allosterically.(2 votes)
- The video doesn't, it's talking in general for most of the ligand gated ion channels and not for any receptor peculiarly. Also neurotransmitters can have a bunch of different kinds of receptors in different places.(2 votes)
- At5:39, what does it mean by the difference in membrane potential? Does it mean the change in energy charged inside and outside of the cell membrane?(1 vote)
- Ions have different amounts of charge that are positive or negative. Membrane potential has to do with the difference in the charge in the intracellular and extracellular space. This difference in charge can determine which direction ions will move (in or out of the cell) when an ion channel opens.(3 votes)
- At the end of video, what does membrane potentials mean in detail? I assume it is not meant the difference in the electrochemical potential?(1 vote)
- Well it's very closely related to electrochemical potential, which takes into consideration the voltage difference as well as the concentration gradient. Membrane potential simply refers to the difference in voltage (read as charge) across a cell membrane.(2 votes)
- can a ligand ever bind to wrong receptor.is there any ligand that can change shape(1 vote)
- Receptors are ligand-specific so they only recognize one (or a few specific) ligands and under normal circumstances will not bind to a ligand different from it's normal set (and vice versa for ligands: they are receptor specific). The induced fit model also plays some role in ensuring the correct receptor-ligand fit because the receptor changes conformation as the ligand begins to bind, and does not become truly complementary to the ligand until this ligand binding begins. As for ligand shape changes, that does not occur again because of the ligand-receptor specificity. Hope that helps!(1 vote)
- So would the channels that allow calcium into a pancreatic beta cell be considered ligand gated ion channels?(1 vote)
Voiceover: Have you ever wondered how our nervous system like our neurons and our brain, can react so quickly? Well, the reason is because of ligand-gated ion channels. Ligand-gated ion channels are one type of major membrane receptors. The three categories are: ligand-gated ion channels, G protein-coupled receptors, and lastly enzyme-linked receptors. Today we're going to focus on the ligand-gated ion channels. These are also called ion channel linked receptors. Ligand-gated ion channels are transmembrane ion channels that open or close in response to the binding of a chemical messenger like a ligand. Like we mentioned, a very common place to find ligand-gated ion channels are in electrically excitable cells like neurons. The reason why is because these ion channels react really quickly to the binding of ligands, and so they're very commonly found in cells that need to react very quickly to stimulus. When we talk about transmembrane ion channels, what we really mean is they are transmembrane or integral proteins that also have a channel, a hole through them, in which things can move in and out. To start out with, let's say we have an ion channel that looks something like this. Let's go ahead and color that in. This particular channel at the moment is closed. Right now, we have our intracellular environment, this is where our cytosol and all of that stuff is. This is our extracellular environment. As you can see, this ion channel has a weird kink in it, and this is a place where a messenger, like a ligand or a neurotransmitter can bind. Let's say we have a ligand that looks like this. This is our ligand. This ligand can bind in there. Notice that the shape of our ligand is complementary to the shape of our channel, so it fits right in there. Only specific ligands can bind to specific channels. This is what we call our "lock and key", or a more updated one is called "induced fit". Once this ligand binds, what it'll actually do is it'll cause this closed channel to actually open up. We'll actually see this channel open up, kind of like that. Now this is our open channel. One really interesting thing about ligand-gated ion channels, is if you look at where this ligand binds, the binding site of this ligand is not anywhere near the actual channel. The reason why is because this is what we call allosteric binding. The ligand binds to what we call an allosteric site. This is a place that's away from the ion channel. But what happens is, once the ligand binds, it can control the opening and closing of the ion channel by altering the protein conformation of the entire protein. Once it binds, a channel opens in a different place, and the ion permeability of the entire plasma membrane can quickly change. Remember this is not just one thing happening. When these ligands are binding, there are many of these channels scattered throughout these cell membranes, so all of these are opening and closing all at once. Once this channel opens it'll let ions, like potassium, sodium, chlorine or calcium being the most common, move through the open channel. Once these ions are moving in and out, this will cause a change in the electrical properties of a cell. In other words, you'll convert this extracellular ligand signal, into an intracellular electrical signal. Once these ions move in, or they can also move out, you'll have an intracellular electrical response, electrical signal happen inside the cell. There are two things I'd like to note real quick. The first is that the allosteric binding site of a ligand, this area that is complementary to the ligand, can be intracellular, it can be inside the cell, but that's considered pretty rare. Why might that be? Well, we'd have to think about the main purpose of membrane receptors. We have to realize that they generally are meant to respond to extracellular signals, to things that are on the outside of the cell. Generally speaking, ligand-gated ion channels will have the binding site on the extracellular side. The second thing to note is that it is possible for there to be multiple allosteric binding sites for ligands. It's possible that there are multiple of these kinks, of these complementary shapes, that let the ligands bind for each protein. Finally, I'd like to clear up two quick misconceptions. Ligand-gated ion channels are easily confused with two types of ion channels. They are not the same as voltage-gated ion channels. Voltage-gated ion channels rely on the difference in membrane potential. As we recall, ligand-gated ion channels actually respond to the binding of a ligand. The voltage-gated ones only depend on the difference in membrane potential. The second one they're easily confused with is what we call stretch-activated ion channels. As the name implies, stretch-activated ion channels depend on what we call the deformation of the cell membrane, or the cell membrane stretching and being pushed and being stressed. In summary, ligand-gated ion channels are one type of membrane receptors. They are transmembrane ion channels that open or close in response to the binding of a chemical signal like a ligand. You'll notice that here our channel is closed, and once this ligand binds to an allosteric site, which is a site that's not on the channel itself, it'll let ions such as potassium and sodium and so on move through the membrane. This will actually cause an intracellular electrical signal. We have one outside ligand, and this will allow us to have an intracellular electrical signal. This will actually tell the cell to do something. Ligand-gated ion channels are not to be confused with voltage-gated channels, which only rely on a difference in membrane potential, and they are not to be confused with stretch-activated ion channels, which are affected by a deformation of the cell membrane.