Amino Acid Classifications - Video Tutorials & Practice Problems
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Nonpolar Amino Acids Concept 1
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Now, here we're going to say that amino acids are classified by the functionality of the R groups attached to their alpha carbon. And we're gonna say they can be classified as either being nonpolar polar or charged amino acids. And when we say charge, we mean that they have a positive or negative charge overall. Now, here we're gonna take a look at our first grouping of amino acids which are nonpolar amino acids. Now remember when we say nonpolar, we're gonna say these, these amino acids contain our groups that are nonpolar and because of that they are hydrophobic. Remember hydrophobic means that you are water fearing and do not interact with water. Now, our memory tool here will help us remember which of the amino acids can be classified as being nonpolar in origin. Our memory tool is Gav trip fell limping. So here I have this friend, his name is Gavin. We call him Gav for short. He's pretty crazy and extreme in terms of ST that he likes to do. Last week, he tried to jump off the roof and do a backflip. He landed in a pile of leaves but somehow broke his ankle. Now he's on crutches. And for the longest time, Gavin has had this fear of the ocean. So he always tries to stay away from water. But here there's a large tsunami that's coming towards him. And Gav in his crutches with his broken ankle is trying to get away. Now, Gav trip fell, limping, running away from the water that he fears. All right. So remember we're gonna use this memory tool to help us remember those amino acids that fall under this memory tool. So when we say Gav, Gav stands for Glycine, Alanine and Valley, remember there are three letter codes here, we'd have GLY and then here Gene Alanine, we have a L A and then a Valle would be V and V. Now let's talk about these. When it comes to Glycine, it's our group is just a hydrogen. Pretty simple. It's the smallest of the 20 amino acids. Alanine is a little bit bigger instead of a hydrogen. It's a methyl. And then we can say that Valle is an isopropyl group instead of a methyl. So get a little bit bigger. Now he tripped, tripped, stands for, tripped the fan here though. So here we're gonna say trip to family members TRP. It is phonetic in origin. It's one letter code is W tryptophan is much larger. We have this large ring as it's our group. Even though it has this n age group here, it's greatly outnumbered by all the carbons within this benzene ring and within this ring portion here as well as the ch two group. So overall, it's nonpolar in origin. Then we're gonna say that it fell, fell with FF. Here stands for pal ay. Remember Pal Allen in here is three letter Kobe phe. It is phonetic in origin. Fennel F pheno Adeline is very similar to tryptophan where we have ach two in both but instead be connected to these two massive rings like tryptophan. We just have it connected to a benzene ring. Then we have what's left we have limping, limping trying to limp away from the tsunami. So limp is leucine, isoleucine, methionine and prolene. All right. So here, if we look at lucine, it'd be L eu and then l we're gonna say ice. Um We're gonna say lucine is very similar here to valle that it has this isopro part right here. But in addition, it has a little bit extra, it has ach two group there isol solution is ile isol solution is I isol. Lucine has these four carbons that make up its R group, which is a S beetle methionine which is met and uses M it has this chain and near the end of it is this sulfur group right here. And so this is a sulfide group right here. So Matin is a little bit different and then prolene is unique because it is actually, it's our group is part of a ring that's with the amino group here. Prolene would be pro and it's one letter would be P, if you were to draw this out straighter, you could kind of see that it forms a letter P the way the ring loops around. So that's another way of looking at the structure to remember that. Oh Prolene almost looks like a pea. It, it loops around itself to make that ring. So remember you have these nonpolar amino acids. My buddy Gavin broke his ankle trying to escape the tsunami. Can't quite move fast enough. Trip, fell, limping. Ok. So just keep this in mind when you have to look at your different types of nonpolar amino acids.
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example
Amino Acid Classifications Example 1
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Here it says, identify all hydrophobic amino acids. Remember when they say hydrophobic, they're really just saying which one represent nonpolar amino acids. Remember our memory tool here will be gav trip foul limping. So here if we take a look at these images, a would be a hydrophobic amino acid because it represents the P within our memory tool. This is prole remember it could be identified by its R group which is this cyclic portion that actually encompasses the amino group. Then what else do we have? We don't recall seeing one which is C H2O H. So that's out we don't recall seeing one with just one ring with an NH group in it. So that's also out. Now this last one here, it's our group is a hydrocarbon. So for sure it's nonpolar because hydrocarbons are nonpolar. This one here would represent isoleucine. So here is so lucine. So out of the options here, it's both A and D, both of them have nonpolar R groups and therefore represent hydrophobic amino acids. So those would be our final answers.
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concept
Polar Amino Acids Concept 2
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In this video, we take a look at our polar amino acids. Now, here they contain our groups that are polar and therefore hydro feli. When we say hydrophilic, it means water loving and therefore interacts with water. We're gonna say all except cysteine form hydrogen bonds with water. And the memory tool that we can utilize to remember which ones are classified as polar amino acids is that Santa's team tirelessly crafts new quilts. So here we have our first letters as well as Tyr tirelessly to help us remember amino acids here. So Santa stands for sir, which is S er and SC here has AC H2O H as its R group. That process of that O age group, we know that it can form hydrogen bonds with water. Next we have 39 which is going to be T hr and then t it too also has an oh group and that oh group is then gonna be overpowered by an abundance of carbons within this R group. There's only two other carbons within this R group. Then we have Tyrece here, Tyr tires here, Tyra, Tyra is phonetic in origin. So it's why this one is larger the CH two group connected to benzene connected to an oh group. We can see a theme developing here for these first three, all of them have oh groups on their R group. Then we have here is cysteine which is unique because here it is a file. Remember a file is an SH group. So CH two sh forms, it's R group. Here it's three letter code would be cys and then here it is unique that it's the only of the 20 amino acid that begins with C which one letter code is C asparagine. Remember this is phonetic in origin. So it'd be a SN. And then N here we have in a my group to complete the last two of these amino acids. Let's talk about um glutamine as well. So GLN and then Q this is also phonetic in origin. Both of these have this end here. An amide end. The difference between them is that asparagine only has one CH two connected to it, but then glutamine is a little bit bigger. So it has two CH two groups connected to that amide group. So this is a way of looking at their similarities and there's slight differences from one another. So remember these are classified as all the polar amino acids out of the 20 that you need to remember. And the memory tool you can utilize here is that Santa's team tirelessly crafts new quilts. OK. So just remember that memory tool to help you organize these different types of polar amino acids.
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Amino Acid Classifications Example 2
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Which of the following amino acids will have our groups mostly on the outside of the protein. So they're, what they're saying here is outside of the protein. And you're assuming that you're in an aqueous environment, a water environment, if you're only the outside, you're gonna interact with the water molecules. So you have to love the water. So you have to be hydrophilic. So what type of amino acids are hydrophilic? The polar ones? So this question is really asking which one of the amino acids are classified as polar amino acids. So if we take a look here, uh we see that our memory tool here is at Santa's team. So ST tirelessly crafts new welts. If we take a look here, which one of these fit with our four options? Oh, here we have is 39, which is one letter code is T. So this is a polar amino acid and therefore be found on the outside of the protein. And then who else do we have? We have GLNGLN is glutamine. Its water code is Q. Here we have methionine which is not classified as a polar one. So this is out, then we have TRP, which is not tyra here. So this would be out. OK. So here we talk about uh tryptophan in this term in terms of this TRP. But tryptophan is not one of our amino acids that are polar in nature. So it would not be found on the outside of the protein. So here are the options B and C as our final, final selections.
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concept
Charged Amino Acids Concept 3
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Now, when it comes to charged amino acids, we're going to say that they represent polar amino acids and they contain our groups that are electrically charged. A physiological Ph meaning they possess a positive or negative charge. Now, here, if we have an acidic R group, we're gonna say it contains a negative carboxylate anion group. And if you're basic R group, then you're gonna be a positive amino group. Our memory tool here is dragons eat Knights riding horses. So if we take a look at this image, remember dragons tend to have a negative connotation attached to them. So the dragons which are negative are connected to our car box like groups, Knights or are positive because they defend us against the dragons, they're positive. They represent the basic groups. So we come here and take a look. We're gonna say here, dragons eat Knights riding horses. The first letters here represent the one letter code for each of these amino acids. Now, here, if we take a look for acidic ones, it's a giveaway when we're talking about their acid forms. Aspartic acid l Amic acid acids. In a name, we know that there are acidic amino acids. So here as carbolic acid, they be, oh but if we're talking about them being a physiological ph, the PH will be high enough that they're gonna lose their H plus. So they actually will exist as a negative in these forms. Their names are now aspartate and glutamate. Here, we're gonna say the one, a three letter code for both of them is, are the same. It would be a SP and then he'd be DD for dragon here. Glutamic acid now becomes glutamate. We're gonna say here this is glue and this is eat, dragons, eat Lyne. Here, Lysne, Arginine and histadine are basic ones. We're gonna say Lysne here is lys, it is different from all the other amino acids because it doesn't use the first letter of its name and it is not phonetic in origin. It uses K as its one letter uh code. So here Knights and so here it has to be positive for it to be positive. The nitrogen has to make four bonds. So it has to be an NH three group here and positive arginine RJ nine depending how you want to pronounce it. We're gonna say A RG, it is phonetic in origin. So R is its one letter code. Again, remember nitrogen needs to make four bonds in order to be positive. So this nitrogen which is already making two would have two more hydrogens histadine. His it is unique. It's one letter code is H nitrogen. Here we see it making three bonds already. So it only has one H on it to make it positive. Now, going back to the acidic ones, we're gonna say that they exist as the conjugate forms of their acidic and basic forms. So, aspartic acid physiological phph is too high can exist as an oh group. It's an O negative group. Same thing with glutamic acid physiological ph, the PH is actually too low for the basic ones. So instead of these nitrogens being neutral, they're gonna have a positive charge. So that's why we have to make sure they're each making four bonds by adding enough hydrogens. So they gain a positive charge on the nitrogen. So remember, these would represent our charged polar amino acids which can be further broken down into acidic and basic amino acids.
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example
Amino Acid Classifications Example 3
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Which amino acid would have a net charge of plus one at physiological Ph. Now remember having a charge around physiological Ph is indicative of a charged amino acid, charged amino acids can be either acidic or basic in nature. If we take a look at all these options, we would say that this is out because this is asparagine, which is not one of our acidic or basic amino acids. This one here it has an R group that is a hydrocarbon. So it can't be acidic or basic, it's nonpolar. And then here we have prolene. Prolene does not classify as a charged amino acid either if we take a look here. The only answer that works is option. A this molecule represents histadine. Histadine is one of our charged amino acids. Remember our memory tool here is dragons eat Knights riding horses. The H here is for histadine at physiological ph. We say that the Ph is low enough that the hydrogen here or the nitrogen here is gonna gain an H plus and become positive. So this negative one is canceled out by this positive one. But then there's nothing to cancel out this positive one. So overall the charges of this amino acid would be positive one and physiological. Ph So here the answer would be option A.
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Problem
Problem
Classify each amino acid as polar, nonpolar, acidic, or basic.
a) Glu
b) Val
c) Pro
d) Lys
e) Gln
f) Arg
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Problem
Problem
Provide one letter codes for amino acids with neutral hydrophilic R groups that participate in H bonding.
A
S, T, Y, C, G
B
S, T, Y, N, Q
C
S, T, Y, C, N, Q
D
S, T, Y, A, Q
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