 Okay, so let's go ahead and attempt to do this problem. We're going to figure out the number of degrees of unsaturation of methionine, which is an amino acid. So the first thing we have to remember is the what? The formula. The formula for? The terminated units of saturation. Well, it's a formula for the acyclic alkane, right? What is that formula, do you recall? I'll help you out. Cn, H2, and plus 2, okay? So you have to remember that formula if you don't remember it. You're going to have a hard time with these. Remember also, whenever we have O's, what do we do to the H's with O's? Do you remember? Okay, so O's we don't do anything to. Doesn't change the number of H's at all. S's, they're below O in the periodic table, so they have the same rules as O, okay? So nothing happens to the H's. So what happens when we have N's in the molecule? You take one hydrogen away. Take one hydrogen away. So what are we going to do? We're going to have C5, H1, 10, okay? So that's the formula that we're looking at now, okay? C5, H10, Cn, H2n, plus 2, right? So if that's the case, it should be C5, H1. 22. 2 times 5. Oh, 10 plus 12. 12, right? Okay, so 12. So what do we do to figure out, well, how many units of the saturation we have? We subtract, right? Always the carbons are going to go away. H2, right? For every H2, that's how many units? One unit or one degree of unsaturation. So that's how many units of unsaturation in this molecule. So that either has one ring or one pipe, okay? And in this case, that's a pipe.