List the amino acids with side chains that are capable of hydrogen bonding. Draw an example of two of these amino acids hydrogen bonding to one another. For each one, draw a hydrogen bond to water in a separate sketch. Refer to Section 8.2 for help with drawing hydrogen bonds.

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All right. Hi, everyone. So this question is asking to consider the pairs of amino acids below A is alanine and valine B is leucine and isoleucine C is glycine and phenylalanine and D is Cine and thine. Part one is or says which pair have side chains capable of hydrogen bonding. Part two says to draw each structure hydrogen bonding to one another. And part three says to sketch each structure hydrogen bonding to water. Now first lets get started by talking about the amino acids proposed in this question. Recall that all amino acids have the same general structure. We have an alpha carbon in the center connecting to both an amino group and a carboxylic acid group. And in addition to these two, we have an R group or a side chain attaching to the alpha carpet. Now, the art group is different for each amino acid and is therefore what distinguishes amino acids from each other. And the properties of the amino acid side chains can help us distinguish the properties of the amino acid overall because we can differentiate between nonpolar neutral polar acidic or basic amino acids depending on what the side chain looks like. But for this question, we're focusing our attention on the ones capable of hydrogen bonding. Recall that in order for a compound to participate in hydrogen bonding, there has to be a hydrogen connecting to a highly electron atom. Specifically, this can be either nitrogen, oxygen or fluorine. So if the side chain of a given amino acid contains a hydrogen connecting to an electron atom, then that side chain and therefore that amino acid is capable of h bonding. Now, if we examine the four pairs proposed in this question, the first thing I want to point out here is that the first three actually discuss or propose nonpolar amino acid pairs because alanine valine, leucine isoleucine glycine and phenylalanine are all nonpolar. These six amino acids contain nonpolar side chains, which means that they are not capable of hydrogen bonding at all. This leaves us with pear D which is serene and threatening. Now recall that Cine and thine both have hydroxy groups or oh groups in their side chains. And this meets the criteria for each bonding, right? Because notice how hydrogen is connected to an electron element, specifically oxygen. So because Cine and thine are capable of h bonding because of their hydroxy groups, we're going to be focusing our attention on these two. So with this in mind, I can go ahead and scroll down a little bit and I can actually answer parts one and two in the same drawing. So the first thing I'm going to do here is to draw the structures of both Cyrene Andreoni. So first I'm going to start off with serene, which has the hydroxy group at the very end of its respective R group. So heres my amino group, this is serene and now I'm going to go ahead and draw out three inning. Now, the difference here is that in the structure of thine, the R group itself is a two carbon chain with the hydroxy group attached to the carbon that is directly branching off of the alpha carbon. So here I'm just completing the structure. And with this in mind, Ive got the structure of three. Now, in this case, it would be relevant for me to go ahead and show the lone pairs of electrons on these hydroxy groups, which is exactly what I'm going to do. Because in this case for depicting this hydrogen bond between these two amino acids, the lone pair of electrons on one oxygen atom is going to interact with the hydrogen connecting to the oxygen atom of the other amino acid. So in the drawing here, I have the hydroxy oxygen of serene using its loan pair of electrons to interact with the hydroxy hydrogen of three. So this would be the hydrogen bond to one another. So now what I'm going to do here is I'm going to go ahead for part three, replicate the same structures for both amino acids. But instead I'm going to depict them hydrogen bonding to water. So the first amino acid I'm going to redraw here is sir, here's my amino group and then I've got three in each to use my carboxylic acid group and my amino group branching off of the alpha carbon. And then here goes my hydroxy group, right. Notice how all amino acids have the same general structure as talked about previously, right? So in this case, what I'm going to do here is first rlabel both amino acids, I've got serine on the left and three on the right. So now what I'm going to do here is I'm going to go ahead and draw water molecules in close proximity to both hydroxy groups. So here after showcasing the lone pairs of electrons on both oxygen atoms, the hydroxy oxygen of Cine is going to go ahead and interact with the hydrogen atom of water. At the same time, the oxygen atom of water is going to interact with the hydroxy hydrogen of three and E and here is their hydrogen bonding to water and there you have it. So here is the answer for parts 12 and three, but parts one and two were grouped together in this case. So what I'm going to do here is just make the drawing overall slightly smaller. So you can see it all in one screen and there you have it. So with all this being said, if you stuck around to the end of this video. Thank you so very much for watching and I hope you found this helpful.

List the amino acids with side chains that are capable of hydrogen bonding. Draw an example of two of these amino acids hydrogen bonding to one another. For each one, draw a hydrogen bond to water in a separate sketch. Refer to Section 8.2 for help with drawing hydrogen bonds.

Verified video answer for a similar problem:

Key Concepts

Amino Acids and Side Chains

Hydrogen Bonding

Hydrogen Bonding with Water