 Okay everybody Dr. O here in this video we're going to talk about the halogens that can be used to as antimicrobials that can chemically control microbial growth. So you see here iodine chlorine and fluorine we're just going to talk about iodine and chlorine. So first of all let's talk about halogens are let's go back to the periodic table for just a moment. So here we have the periodic table so the halogens there you see the iodine chlorine and fluorine. So halogens are in group 7A on the periodic table which means they really really want an electron because they want to behave like the noble gases they're sitting next to. So they're going to be scavenging and pulling electrons from anywhere that they can. That's actually so that's important because that's how they work. So I'm going to go back to the first page here. So they work by oxidation so remember oxidation is removing electrons from something. So halogens are going to bump into things and what really matters here is like it says they're the destabilization of cellular macromolecules. So halogens are going to bump into things like sulfur containing amino acids, your nucleotides that make up your DNA and RNA, et cetera. Fatty acids like in your your phosphoid bilayer of your cell membranes and it's going to oxidize them. It's going to pull electrons away from them which is going to destabilize them. So it's basically this oxidation effect that comes from where they're sitting in the periodic table is what makes them work. As you see lots of different examples here so let me go ahead and give you a couple of them when we jump back into. So so here we see a betadine being used. So betadine is actually an iota for and that's going to be when you take iodine and mix it with organic molecules and that's going to make it more stable and it's going to be able to persist longer. So that's why it makes it more effective. You can also find halogens mixed in tinctures with alcohol but the iota for is the most important one. So here we see betadine it's an iota for it's called provodone iodine and it's very effective on on skin. So there's an example of using iodine on skin. All right and then we see chlorine obviously when you think of chlorine especially in a microbiology class we should think of water treatment. So it's kind of neat how chlorine works. So when you take gashes chlorine and mix it with water it forms a powerful oxidant called hypochlorous acid and that's the key right the chlorine gas isn't antimicrobial in that form when it becomes hypochlorous acid that's when it becomes very antimicrobial so that's why we add chlorine to our water to chemically treat it. One last thing to note here about hypochlorous acid is is uncharged which basically means that it can move in and out of cells just like water does and that's what allows it to get inside of get inside of cells. So that would be the chlorine used for water treatment becomes this hypochlorous acid that is antimicrobial. So you did like like sodium hypochlorite would be one of the key examples there and well sodium hypochlorite is actually what's in bleach so the same thing. So treating your water using bleach this it forms this hypochlorous acid then you have this strong oxidation reaction that kills the microbes. If you've ever if you've ever lived somewhere where they've put as much chlorine in your drinking water as they can and there are other ways to treat water we'll cover that in separate videos like using ozone and stuff but if they've added all the chlorine they can to your water what they will then add is chloramines. So chloramines are actually going to be more stable so they're going to release chlorine over longer periods of times. So what you see here is a chloramine is ammonia where these hydrogens are going to be replaced with chlorines that's what a chloramine is. So the reason that you would then you would use them in water if you needed to is because they do persist longer. So if you can't kill all the contamination in drinking water with chlorine you would add the chloramines. So one just kind of little neat or added bonus bonus right word for it but if they do have to put chloramines in your drinking water they usually send out strong warnings not to use this kind of water in your fish tanks. Now chlorine can hurt fish too so obviously you can remove that but since chloramines persist longer way more likely to kill your fish and that's why if you have fish tanks you buy those chemical treatments that remove the chloramine and the chlorine from the water. Okay all right so those are your two clinically significant halogens iodine and chlorine and I hope this helps have a wonderful day be blessed.