Now, we also have a fourmember ring here that's called the Betalactum. And it's the instability and the high energy of the beta lactamb that actually gives that penicillin a reactive nature and allows it to actually react in the first place. In fact, it's this red carbon in the betalactam ring that allows it to react as we'll see towards the end of the lecture. And finally, the final component of penicillin is this r group. So it's the r group, it's the variable r group that basically gives that penicillin its unique structure. So penicillin is actually a group of many related molecules that all contain the thiozolidine ring, the Betalactum ring, as well as that unique variable r group.