Draw the structure of the possible dipeptides formed from one alanine combining with one cysteine.

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All right. Hello everyone. So this question is asking us to draw the structures of the dipeptide that can be formed when the following two amino acids are combined. And here we have one siren and one alanine. So first and foremost, because we only have two different amino acids to arrange for this peptide, we have a total of two different di peptides to draw. And so let's talk about the conventions to keep in mind when drawing out a peptide. And the first one, if you recall is that a peptide should always be written from the N terminus to the C terminus. So what this means is that on the left side, you should have the amino acid written that has the free amino group. On the right side, you should have the amino acid that has the free carboxyl group. So let's go ahead and start with the peptide bond backbone of both of these peptides because that's not going to change. So here, according to our convention, right, the N terminus, so the free amino group should be on the very left side of the structure. So that's what I'm drawing here. And so from there, the pattern is going to be much the same. Next to the amino group, we have our alpha carbon that contains our side chain with an extra hydrogen. And on the other side of that alpha carbon is the carbon carbon of the carboxylate group. But recall that amino acids in a peptide are held together by peptide bonds which are m linkages. And so because here we are proceeding now to the next amino acid instead of drawing the hydroxy group of this carboxylic acid, this carboxylate group, the carbo of the first amino acid is combining now with the amino group of the second amino acid. But despite this, the pattern remains much the same because from the nitrogen, we have the alpha carbon and from the alpha carbon, we have the car bono group. And this time because we've reached the end of the peptide itself, we have arrived at our c terminus. So it should be a carboxylate. And so because this peptide bond backbone is going to be the exact same for both answers that we're going to draw out here. I'm just going to go ahead and copy paste, what I just drew. So now the main difference is the order in which these amino acids are arranged in the peptide. So there are two different possibilities. One in which alanine is the first amino acid sine is the second and the other where it's backwards, right Cine is instead the first amino acid and alanine is the second. So let's start with that first possibility where alanine is first like the alphabetical order, right? So to go ahead and take that into consideration, all I would need to do is add the side chain of alanine to the alpha carbon. Farthest to the left. The side chain of alanine is a methyl group. So that's all I need to add to our first alpha carbon. Now, the second alpha carbon belonging to Cine in this first peptide should contain ach two group followed by a hydroxy group. So here we have here we have alanine followed by a Siri. So now let's draw, sir, followed by Alan. Now the side chain of seine should be on the alpha carbon furthest to the left. So I said C H2O and so alain, the methyl group of Alaine should be on the second alpha carbon and there you have it. So here are our two dye peptides. So once again, the reason why we end up with two different di peptides is because there are only two different ways we could arrange these amino acids. And so with that being said, if you watch this video all the way through, thank you so very much. And I hope you found this helpful.

Draw the structure of the possible dipeptides formed from one alanine combining with one cysteine.

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Key Concepts

Amino Acids

Dipeptide Formation

Peptide Bond