018 Agonists and Antagonists

hello and welcome to another episode of interactive biology TV where we're making biology fun my name is Leslie Samuel and in this episode episode 18 I'm going to be talking about agonists and antagonists it's almost sounds like a plot for a movie but it's not a movie unless it's a movie happening inside your body anyhow for today let's get into what we're going to be talking about the first thing we're going to talk about is what is an agonist and an agonist is a molecule that mimics the effect of a neurotransmitter so it does what that neurotransmitter would normally do an example of that would be succinylcholine mimics the neurotransmitter acetylcholine so what I'm going to do is I'm going to draw again I'm going to draw the receptor here and here we have the cell membrane of the neuron and I'm going to draw it a little different than I've been drawing it before I'm going to have this as the receptor sites this is where the acetylcholine normally binds to the nicotinic receptor I'm going to draw acetylcholine here but I'm not going to draw it coming here what I'm going to do is I'm gonna draw something that's slightly different let's just say it's a different color but it has a similar shape as a siedel choline and we're going to call this succinylcholine when that comes here and it binds to the receptor same thing here comes and it binds through receptor the channel opens which is what it would normally do if acetylcholine binds and then sodium ions on the outside end up coming inside the cell so this would be an example of an agonist it's not a cetyl choline it's something else and let's say in this case it's succinylcholine and that comes binds to the receptor and causes a similar response that is an agonist now let's look at what an antagonist is and you can probably guess just by reading the word but an antagonist is a molecule that opposes the effect of a neurotransmitter so it does the exact opposite and an example of that would be curare which is an antagonist to acetylcholine that can actually block the binding sites for acetylcholine so here we have our nicotinic receptor again and it's in the membrane of the cell and here we have the binding sites and out here we have acetylcholine that wants to bind however we have something else that's around that's not exactly like acetylcholine and let's say that its shape looks something like this and that binds to the receptor and what that does is it blocks the receptor site so acetylcholine wants to bind and it wants to cause that channel to open but it's being blocked so that it cannot bind and it cannot open the channel for sodium to come in this would be an example of what curare does it's an antagonist and in fact qre can cause muscles to become paralyzed because they cannot be activated and sodium cannot rush into the cell exciting the cell and exciting the muscle to contract so that can be a serious thing if you have curare binding to these receptor sites that's really all for this video I hope you understand the difference between an agonist and an antagonist if you have any questions or comments about that go ahead and leave them below I'll be happy to answer your question and maybe even make a follow-up video answering your specific question that's it for this video and I'll see you in the next one