Polar Amino Acids - Video Tutorials & Practice Problems
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Polar Amino Acids
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In this video, we're gonna talk about our 3rd group of amino acids, the polar amino acids. So the polar amino acids all contain r groups that are hydrophilic. And recall what we mean by hydrophilic is just water loving, and that's due to the presence of terminal electronegative atoms or electronegative atoms that are found at the very ends of the r groups and are easily able to interact with water, making them hydrophilic. Now polar amino acids also contain hydrogen bonding groups, so the r groups of polar amino acids are capable of forming hydrogen bonds and there are 5 amino acids that are grouped as polar amino acids and those 5 amino acids are serine, threoninecysteine, asparagine, and glutamine. And so down below, we have a mnemonic to help us remember those 5 polar amino acids. So when you're thinking about the polar amino acids, you really wanna be thinking about the North Pole. And who's in the North Pole? Santa, duh. And so every winter when it gets cold, Santa and his team, they craft new quilts in order to stay warm. And literally, that's our mnemonic. Santa's team crafts new quilts, where the first letter of each of these words symbolizes the one letter code for the corresponding polar amino acids. And so what you'll notice is down below in our image, we have a picture of Santa, a picture of Santa's team, these little elves, a hammer here for the crafting, and then a quilt, a new quilt. Not an old quilt, a new quilt. And so down below, we And so, down below, we're actually going to talk about each of these individual R groups on these amino acids in the blocks. And so in the block on the far left over here, what we have is serine. And serine's three letter code is just s e r, and its one letter code is just an s. And so you can see how the s for serine here and our mnemonic, it's being represented as Santa. Now, in our next block, what we have is threonine, and threonine's three letter code is just t h r, and its one letter code is just a t. And so you can see how the t here for threonine is being represented by the team in our mnemonic. Now, one way to help us remember part of both serine and threonine structure is to remember that alcohol is a serious threat. And so the SER in serous is for serine and the 3 in threat is for threonine. And so by remembering that alcohol is a serious threat, that can remind us that serine and threonine both have alcohols in their r groups, and alcohols are literally just Oh groups or hydroxyl groups. And so looking up above at our image, we know that Santa here is representing serine and notice that Santa has a little beer in his hand. He has a little bit of alcohol in his hand. And also notice that the team, which is representing, threonine, also has these little beers in their hand. They have these little alcohols. And so again, that can remind us that both serine and threonine have alcohols in their r groups, and they're the only 2 amino acids of these 5 amino acids that actually have alcohols in their r groups. So when we go to draw their structures, we're going to be looking for alcohols. Now, even though Santa and his team, they know that alcohol is a serious threat, they also know that if they have it in moderation, it's okay while they're crafting their new quilts. So, notice that serine here, the s, is the leader for the polar amino acids because it's the first one in our mnemonic. And so serine is literally just gonna be following our leader amino acid alanine, which we know alanine is the leader amino acid from our previous videos. And so literally serine is just alanine with an alcohol group with an alcohol. And so, what you'll see is when we're drawing serine's, r group, we're literally just gonna draw, alanine, so it's gonna be c h. And we know that the number of hydrogens are going to change, it's going to end up being just 2, and then it's just going to have an alcohol branching off or an o h group. And that is it for serine structure. So moving on to threonine, threonine structure is really based off of serine structure. And really, it turns out that threonine is just serine with an extra methyl group. And so looking at, threonine structure, we can draw in a part of serine structure, so the carbon with the alcohol coming down. We know that there's gonna be, one hydrogen over here, but instead of having 2 hydrogens like serine, one of those hydrogens is replaced with a methyl group of c h 3, and that is it for theanine structure. And so another way to be able to remember theanine structure is that the threonine, reminds us of 3. And so that can, remind us that threonine has 3 parts on its only central carbon, and those three parts are a hydrogen atom, a alcohol group, and a methyl group. And so the threonine can remind us that there are 3 parts on the only central carbon, and that's another way to be able to remember threonine's structure. So now that's it for serine and threonine's R groups, let's move on to cysteine. And so cysteine's three letter code is just c y s, and its one letter code is just a c. And you can see that the c here for cysteine is being represented by the crafting hammer here. And so this crafting hammer likes to spend quiet time in the Sistine Chapel. And if you don't know what the Sistine Chapel is, it's literally just a church. So when you're thinking about polar amino acids, you think about the North Pole, you think about Santa, you think about Christmas, you think about churches. And so Sistine spends quiet time in this Sistine Chapel Church. And whenever somebody makes a noise, Sistine is always just like shh. And so literally, cysteine is just our leader amino acid alanine with a sh group, an s h group. And so all we need to do to draw a cysteine structure is to just draw alanine, so c h. We know that the number of hydrogens are gonna change, it's gonna end up being just 2, and then it's just gonna be alanine with a sh group coming off, an s h group. And that is it for cysteine structure. And so, we can move on to our next amino acid, which is asparagine. And so asparagine's three letter code is just a s n, and its one letter code is just an n. And we can see that the n here is the asparagine is being represented by new in our mnemonic. And so, turns out that asparagine is literally just alanine, our leader amino acid, with an amide group. And recall that an amide group is literally just when you have a carbonyl group with a nitrogen coming off of it. And so this is an amide group. And so, we know that, the one letter code for asparagine is an n, and so the n can remind us of the amide. We can say that the n is essentially equal to the amide here. And so one way that this n can remind us of the amide is that n's stand for, nitrogens. So we know that there's a nitrogen and an amide. And also n's, they have these 2 parallel lines. They've got this parallel line and this parallel line, which reminds us of a double bond and we know that amides have a nitrogen as well as a double bond with the carbonyl group. So when we're drawing a spargene structure, we're gonna start off with just drawing alanine, and so alanine is just c h, and we know that the number hydrogens are going to change, it's going to end up being just 2. And then it's alanine with an amide group branching off, so a c double bond o with an n h 2. And that is it. So you can see that we have our amide group here and it's literally just alanine with an amide group branching off and that's it for spargene structure. Now moving on to our last amino acid in this group, we have glutamine, and glutamine's 3 letter code is just g l n, and its one letter code is just a q. And so the q here is represented as, quilts in our mnemonic up above. And so, when it comes to glutamine, what you really want to focus on are these glutes, this glute part. And so, some of you may or may not know that the gluteus maximus is commonly known as your glutes. And the gluteus maximus or your glutes are just your butt cheek muscles, your butt muscles. And so, when you're thinking about gluteamine, it has that glute in it. So you wanna imagine, what happens if you don't have the glutes. Well, if you were missing your glutes, with this x here, if you don't have your glutes, you're straight up just gonna be missing your entire butt section. And if you're missing your entire butt section, you're just gonna be straight up shorter. You're just gonna be so short because you're missing your whole butt section. But if you actually have your glutes with a check mark here, you're just going to be pretty tall. You're just going to be taller with your butt section, and the butt section, the glute here, is really just a methylene group, a CH 2 group. And so, because, glutamine actually has the gluten in it, we know that it's gonna have its butt section. It's gonna have this methylene, this extra c h two group. And so, it turns out that glutamine is really just branching right off of a spare gene structure. And so glutamine is literally just a spargene with an extra c h 2 with an extra glute, some extra butt section, some extra c h 2. And so when we're drawing glutamine structure, we're gonna draw a asparagine exactly but with an extra c h 2. So we'll have 1 c h 2, an extra c h 2, and then we'll have our amide group. And so that's exactly what we can see. We can have an amide group, and essentially it's exactly the same as asparagine except we have an extra c h two, this extra butt section that is missing from asparagine. And so that is it for glutamine structure. And there are a lot of different memory tools that we have to memorize the polar amino acids and we'll be able to get practice utilizing all of these memory tools in our practice video, so I'll see you guys there.
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Problem
Problem
Draw in the R-groups from memory for each of the polar amino acids.