Some of the most important organic compounds in biochemistry are the α-amino acids, represented by the general formula shown.
Write structural formulas for the following α-amino acids.
(f) Cysteine (R = XCH2 , where X is the functional group that characterizes thiols)
Hey everyone, let's take a look at our question, here we are asked to draw the structure for a cysteine molecule, so remember that amino acids are going to be in this general formula but the R group is going to vary based on the amino acid. So, in cysteine we're going to say that our R group is going to be an XCH2 where X represents a thiol, so what does the thiol functional group look like? Well, we can say it's an SH, right? So here in cysteine all you need to do is take a look at our general formula for an amino acid, it looks something like this and remember that for cysteine we said we're going to have first a CH2 group, so let's write that in, we have CH2 and then what do we need? we need SH, okay? So, each aminoacid is going to vary slightly, so it will pay off in the long run specially when you take biochemistry to remember each R group and associated with the name of the amino acid, for instance, if we have serine, serine would be very similar to our cysteine except in serine we have an alcohol instead of a thiol. So, just remember now when we're talking about cysteine we just have to remember XCH2, where X here in this case happens to be a thiol, okay? So this is the structure for it and I hope this makes sense.