Draw the structures for the amino acids under these...

Draw the structures for the amino acids under these conditions: a) Arg at pH 7.2 b) When this polar but uncharged R group is hydrolyzed, this amino acid is converted into another amino acid having a negatively charged R group at pH 7.

Transcript

00:01 We have two questions here where we have to discuss, or draw two amino acids.

00:07 The first one just wants to draw arginine at ph 7 .2.

00:14 So argenine, we can get the basic structure of an amino acid down first before we can worry about the side chain.

00:28 And so now we go on to the side chain from here, and this is actually coming up towards us.

00:32 And then one, two, three, we have the first nitrogen group, then that branches off into two more nitrogen groups from this carbon here.

00:54 And the pkk of this one here is 12 .1 pk, which means, so it's protonated, so it's deprotonate state, we'll just have 1h there, but below 12 .1 pk, we get that second proton there, which gives it a positive.

01:12 So this is arginine at 7 .2.

01:18 It's going to be protonated and in the charged state as a result of the ph being below the pca.

01:38 So the second one is a bit trickier.

01:40 We have to figure out which amino acid this is.

01:44 And so what i'm going to start with, which amino acids have a negative charge at p87.

01:50 Well, there's only two amino acids that fit that bill.

01:56 The first one is going to be aspartic acid.

02:13 It has a negative charge because it's pga is 3 .71.

02:20 And the second one is glutamic acid, which just has one more carbon and the chain.

02:39 So we have spartic acid, glutamic acid.

02:52 And this pkk is a little higher at 4 .15, but both of these, negative at ph 7...

Question

Draw the structures for the amino acids under these conditions: a) Arg at pH 7.2 b) When this polar but uncharged R group is hydrolyzed, this amino acid is converted into another amino acid having a negatively charged R group at pH 7.

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