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 going to say they can be classified as either being non-polar, polar, or charged amino acids. And when we say charged, we mean that they have a positive or negative charge overall. Now here we're going to take a look at our first grouping of amino acids, which are non-polar amino acids. Now, remember, when we say non-polar, we're going to say these amino acids contain r-groups that are non-polar, 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 non-polar in origin. Our memory tool is Gav Tripp 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 the sense 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 Tripp fell limping, running away from the water that he fears. Alright. So remember, we're going to 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 valine. Remember, their 3-letter codes here. We'd have glycine—gly, and then g; alanine—we'd have ala, and then a; valine will be val and v. Now, let's talk about these. When it comes to Glycine, its r-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 Valine is an isopropyl group instead of a methyl, so yet a little bit bigger. Now, he tripped. Tripped stands for tryptophan here though. So here we're going to say tryptophan, remember it's trp. It is phonetic in origin, its one-letter code is w. Tryptophan is much larger. We have this large ring as its r-group. Even though it has this NH group here, it's greatly outnumbered by all the carbons within this benzene ring and within this ring portion here, as well as the CH2 group. So overall, it's non-polar in origin. Then we're going to say that it fell. Fell with f. F here stands for Phenylalanine. Now remember, Phenylalanine here, its 3-letter code is phe. It is phonetic in origin, phenyl f. Phenylalanine is very similar to tryptophan, where we have a CH2 in both. But instead of being 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 Proline. Alright. So here if we look at Leucine, it’d be leu and then l. We’re going to say Leucine is very similar here to Valine, that it has this isopropyl part right here, but in addition, it has a little bit extra, it has a CH2 group there. Isoleucine is ile. Isoleucine is I. Isoleucine has these 4 carbons that make up its r-group, which is a sec-butyl. Methionine, which is met and uses m. It has this chain, and near the end of it is this sulfur group right here. So, this is a sulfide group right here. So Methionine is a little bit different. And then Proline is unique because its r-group is part of a ring that's with the amino group. Here, Proline will be pro, and its 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 this structure to remember that, oh, Proline almost looks like a p. It it loops around itself to make that ring. So remember, you have these non-polar amino acids. My buddy Gavin broke his ankle trying to escape the tsunami, can't quite move fast enough, trip fell limping. Okay. So just keep this in mind when you have to look at your different types of nonpolar amino acids.