So remember, in our discussion on Irreversible inhibitors, we said that penicillin is essentially an antibiotic. And this penicillin molecule binds into the active side of a specific type of enzyme used by bacterial cells to build bacterial cell walls. And this enzyme is known as transpeptidase. So bacterial cells use trans peptidase to basically build cell walls. And what penicillin does is it acts as a suicide inhibitor, that is, it binds into the active side of that enzyme, and it begins the catalyzation process. But somewhere down that line, it forms an intermediate that essentially blocks and inhibits the activity of that enzyme, the transpeptidase.