3. Amino Acids
Non-Ionizable Vs. Ionizable R-Groups
Non-Ionizable Vs. Ionizable R-Groups
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in this video, we're going to distinguish between non ionized, able and ionized able are groups so non ionizing are groups are basically just are groups that are uncharged and so recall that an ion is just an atom or molecule with a charge. And so if you are non ionized herbal, what that means is that you are not capable of gaining a charge. And that's because these our groups are lacking acid base reactions or proton track transfers. They lack those, and that's why they're uncharged and non ionizing ball. And so amino acids that have non ionized able are groups. They only have two PK A values one for the amino group and one for the car boxing group. But they do not have a third PK a value, for there are groups, so there are group does not have a peek A and so really there are actually 13 amino acids that have non ionizing ble are groups and we'll see those in our example below now really quickly. Let's talk about ionized able, our group so ionized well, our groups are essentially the opposite of non ionizing Volare group, so I invisible are groups are charged groups that result from acid base reactions, or H plus or proton transfer. So they do have these reactions. And so because, uh, invisible are groups are capable of ionizing and gaining a charge. They amino acids that have ionized are groups have three p k a values because the our group does have ah, PK. And so, uh, the ionized able are groups are all capable of forming ionic bonds, and that's a really big distinct distinction between amino acids. Within Izabal are groups and amino acids with non ionizing Balart groups, because amino acids with non ionizing Balart groups are not able toe form Ionic bonds, and that's 13 the vast majority of them that are not able to do that. And so, in our example, what we're gonna do is we're going to total the total number of amino acids that fall into each of the indicated ionization groups. So we've got all of these groups in the color code shown and the right here. And so in this chart, what you'll see is that the pink all of the pink colored ones are positively charged amino acids at physiological pH. Ph. Of seven. And so recall from our pneumonic dragons eat nights riding horses that the knights riding horses are the positively charged basic amino acids. And so there are three of them. So Argentine. So these are in alphabetical order. So we have Argentine history ing and licensing, which are these three here. So there are three amino acids that are positively charged at Ph. Seven and with the negatively charged at Ph. Seven, we know that the dragons eating those are the D and the those are the negatively charged acidic amino acids, and so they are negatively charged at Ph. Seven. And of course, those include a Spartak acid and glue tannic acid or Asper, Tate and glutamate. And so those are in yellow and you can see those here a Spartak acid and glue tannic acid. And so there are two amino acids that fall into that group. And then finally, there are some amino acids that are still ionized bull, but they're actually uncharged at physiological pH, which is why we don't have them grouped up here with our charged amino acids at physiological pH and those two amino acids that can become charged but at a different Ph. Other than physiological pH our Sistine, which is found here and tyrosine. And so there are two amino acids here that fall into that group. So there are a total when you add these all up from each of these groups, there are a total of seven amino acids that are ionized herbal. And that means, of course, that the the rest of them the rest of the 20 are going to be non ionized. Well, so again, there are 13 amino acids that are non ionizing Bill and not capable of gaining a charge. Now, what I want to do before we move on is to take a look at these ionized well, but mostly uncharged at physiological pH. And those are Sistine and, uh, tyrosine. And so with Sistine recalled three letter code A. C. Y. S. And it has a self hydro group just like this. This is It's our group. And so notice that Sistine it's our group PKK, which is shown in this column over here. It's our group. P K is 8.3, so we can put that in over here. And so when the pH is above 8.3, what will happen is, uh, Sistine. Our group is going to donate its hydrogen and gain a negative charge just like we see here. And so it's important to be able to recognize that, uh, sister, how Sistine Ionized is, uh, since we already know how the other five ionized because we memorize their structures when they were ionized. Uh, it's important to memorize specifically how these guys ionized since we already know how the positive and negatively charged ones ionized. And so the other amino acid that falls into this group is tyrosine and notice tire scenes. Uh, PK is 10.1. So when the Ph is above 10.1, uh, Tyra scenes are group will donate its hydrogen and gain a negative charges. Well, so it's important to recognize how these two ionized as we move forward in our practice problems and our next topics. And so this concludes. Our lesson on the distinction between non invisible and I invisible are groups, and I'll see you guys in our practice videos
Which pair of amino acids could form an ionic bond between the R-groups?
Asp & Glu
Gly & Leu
His & Arg
Cys & Lys
Memorizing Amino Acids With Ionizable R-Groups
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So now that we know that there are only seven amino acids within Izabal are groups You might be looking for a strategy to not only memorize the seven amino acids, but also the nature of the ionization. For those are groups themselves in terms of will they gain a positive charge when they're ionized, or will they gain a negative charge when they're ionized? And so the good thing is that of these seven amino acids, it actually includes all of the charged amino acids that we already memorized in our pneumonic dragons eat nights riding horses. So it includes those five in addition to the two that we talked about in our previous lesson, tire seen or why, and Sistine or C. And so in our example, we have the pneumonic to help us memorize all seven of those amino acids and the nature of their organizations. And so the pneumonic is just an extension toe what we already know, and it's just yucky. Crazy dragons eat nights riding horses. And so, um, basically, what we've added here is tire seen insisting with yucky and crazy and so yucky and crazy are both negative words. You can't really think of something positive when it comes to yucky crazy dragons trying to eat you. And so, uh, notice that these all have negative charges. So there's a negative charge here is well, so the only ones that have a positive charge are the ones, uh, with the Knights riding horses, because again they're noble. They're coming to save the day in their positive. But there's nothing positive about yucky crazy dragons trying to eat you, so they're all negative. And again, there's a distinction between the yucky and the crazy, the tire seen in the Sistine from the dragon's eating, even though they're both negatively charged. There's a distinction, and that's shown by the blue shade and the yellow shade. And so the blue shade. The difference is that these tire seen insisting, are uncharged at Ph. Seven at physiological pH. Their uncharged. And that's why we didn't group them originally with the charged amino acids, which are all charged around physiological pH. But even though tyrosine insisting again are uncharged at physiological pH, they are likely to be ionized and gain a charge at other pH is. And so that's why we've got this pneumonic to help us memorize them. And so hopefully this will help you guys with a memory tool and we'll be able to utilize it as we move along through our course. So this concludes this lesson and I'll see you guys in our next video.