Histidine house, a Tire in Tyrosine, Phenyl ON alanine? These are just some of the memory tricks you're about to learn to help you finally know the 20 common amino acids and their side chains. Amino Acids contain an alpha carbon, a Hydrogen a carboxy group and an amine, we will use the zwitterion for both and the variable side chain R. Don't just watch this video, work with me. Pause the video, draw the structure, watch it again, draw it again and again until you have it. Let's start with non-polar amino acids. Remember that Great Ambitions Vanish Limitations Inspiring Tired Future Medical Professionals to remind you of your non-polar amino acids. Glycine, that's Gly first letter G does not have an R-group, just a hydrogen for a total of 2, which makes it achiral. Since there's no side chain, we can't say that it's hydrophobic or hydrophilic, it just isn't. Alanine is Ala first letter A, the first letter in the alphabet and the smallest amino acid side chain which is just the CH3. Quick tip for the upcoming amino acids, they all start with alanine. Turn the CH3 to a CH or a CH2 allowing for additional groups but they all start with this line. The straight chain makes it Aliphatic and having just carbon and hydrogen makes it hydrophobic. Valine has an isopropyl group which is an upside down V or Val or V. Leucine, first three letters Leu abbreviated L, is a little tricky. We said every amino acid has a CH2 drawn like this in line structure, then add the L and connect them. Do you recognize an isobutyl side chain? Leucine is Aliphatic and hydrophobic. Isoleucine is an iso, a constitutional isomer of Leucine. And instead of taking the first three letters, we take the I for Isomer, le for Leucine, with a one letter name of I. As an Isomer of L we'll draw the L differently and then add an I. I L E, an I on L. Do you recognize the sec butyl group? Isoleucine is Aliphatic and Hydrophobic with a second chiral center in the side chain. Methionine first three letter Met abbreviated M has a sideways M for its side chain with a sulfur before the end. The eukaryotic start code on Aug codes for methionine. Methionine is aliphatic and hydrophobic. Phenylalanine kinda sounds like phenyl on alanine. So we start with alanine because they all start with CH2 and then add a phenyl. Phenyl and carbon is actually a benzyl group. The first three letters are p h e. But the p is already taken by another amino acid, so we sound it out. P h e, Fe, sounds like an f, giving me f as the abbreviation. The benzene ring makes it aromatic and hydrophobic. Tryptophan is a tricky amino acid that always trips me up. Here's how I draw it. Start with alanine because they all do. Add a five member ring. Connect a six member ring, put a nitrogen at the pointy bottom and give it a hydrogen, fill in your pi bonds and hey, you got it. Tryptophan always trips me up and I say, whoops. That's t r p for trip and w abbreviating, whoops. Notice the two funky w's? MCAT students, with a multiple choice exam, you can get away with just knowing that it's the only amino acid with a bicyclo ring. And these rings also make it aromatic and hydrophobic. Proline is a tricky one because it involves the amine group on the parent chain. Notice how it swings back around just like the letter p. This helps me remember the three letters p r o and their abbreviation p which swings back around just like the structure. With only carbons and hydrogens, proline is hydrophobic. Polar amino acids are tricky because they're mostly hydrophilic. Remember that science teaches curiosity that awakens genius to help you remember the polar amino acids. Serine is a simple alcohol. If we always start with alanine, what's the simplest alcohol I can draw? Just add an OH. The first three letters are SCR and the first letter is S. Simple, right? The OH group makes Serine Polar and Hydrophilic. For Threonine, think Three-OH-nine. The first three letters are T H R, first letter T, where the three tells me that I have three groups. Start with alanine, a methyl group and then the OH, the alcohol. The alcohol makes it polar and hydrophilic. Threonine is the second amino acid with a second chiral carbon. Tyrosine is another alcohol that gives away the structure in the name. Think of it as Tire- OH- sine. That's a CH2 because they all have it. Add a tire, a benzene ring. And OH, an alcohol. That's a Tire-OH. See? The first three letters are t y r, but we can't abbreviate t, that's threonine, so we'll take the second letter Y. Is tyrosine hydrophilic? Not really. Yes, the alcohol makes it polar. The benzene ring is so much bigger and so scared of water, it's borderline hydrophobic. And of course, it's aromatic. Cysteine, first three letters, CYS abbreviated C, can be drawn exactly as we name it. C and S. We add the C that's alanine, so they all start with it, and add an S with an H. Cysteine is another tricky one. It's hydrophobic and just barely non polar. Polarity happens with an electronegativity difference of 0.5. Here we have .38, which is just barely nonpolar. Note that cysteine can use the sulfur to form disulfide bridges. Asparagine and glutamine are both amides, so let's learn them together starting with asparagine. All R groups begin with a CH2, then just add the amide which is a carbonyl with an NH2. For glutamine, since G comes after A, glutamine gets a second carbon and then the amide. The amide has a non reactive resonating nitrogen making it partially charged and polar but not strong enough to grab a proton. What about their abbreviations? Asparagine takes the start and end, ASN, where the N reminds me of the amide's nitrogen. And the same with glutamine, the first two GL, and again N for the amide. The first letter is tricky. ASN comes first, so it gets to claim the amide's nitrogen. While we can't use G for GLN, we can get close. Think qutamine, just close the G and you get a Q. They're both quite polar and therefore hydrophilic. Acids are proton donors. Amino acids have a carboxy group that donates a proton at low pH. That means we have a negative carboxylate at physiological or the mid pH ranges. Basic amino acids will accept a proton on their basic nitrogen to give a positive nitrogen at the middle pH ranges. Or just remember, acids give away and bases adopt lonely hydrogen to remind you of the acidic and basic amino acids. Remember asparagine and glutamine? If I swap their NH2 for an OH, I get a carboxylic acid. Asparagine gives me aspartic acid, and glutamine gives me glutamic acid. In fact, this is a transamination reaction. Since acidic amino acids are deprotonated at physiological pH, the conjugate bases are aspartate and glutamate. Their three letter names are easy. Just take the first three letters, A S P for aspartic acid and GLU for glutamic acid. But they're one letter abbreviation, what are we even left with? For aspartic acid, think “aspardic” acid, giving me a D.Glutamic acid is already abbreviated to GLU, so just spell it correctly and add the E. Or think e comes after d and glutamic acid is slightly bigger or follows aspartic acid. I find basic amino acids tricky, so remember this. The word base has four letters, all basic amino acids have four carbons, and nitrogen makes it basic. Lysine is easy. The first three letters are LYS but we've already used L for leucine. Okay. We'll use something else. Okay. We'll use K. We know it's 4 carbons so just draw them in a row, add your basic nitrogen, fully protonated a physiological pH, and you have your NH3+ Arginine, the pirate amino acid. Arg! says the pirate. A r g, which sounds like, arr, giving me the abbreviation. Because yes, Arrrr! It's so confusing to draw. I want you to imagine a pirate ship's anchor. The anchor is a Guanidinium group. That's a carbon with three nitrogens around it, either end can get the double bond. And since we know base equals 4 and we already have one carbon, add three more for the rope to give me the side chain. Add two hydrogens to lower nitrogens, one to the upper, and the one with too many bonds gets a positive charge. Lastly, Histidine Has an easy name. First three letters, HIS abbreviated H. So let's draw it. Every R group starts with a CH2 and then remember H for house. That's a five member ring house where nitrogen with a lone pair is our window, give them both hydrogen, fill in your pi bonds and the one that doesn't have a lone pair is your basic nitrogen. Why this one? It has 4 bonds, no lone pairs, and a formal charge of plus one. How did I know to put the charge here and at what pH will the proton come off? That's exactly what I teach in my zwitterion video here, which you can find on my website along with my amino acid practice quiz and cheat sheet at leah4sci.com/aminoacids linked below. Links and Resources mentioned in this video: leah4sci.com/aminoacids