So once again, that peptiglycan cell wall that we're going to discuss in just a moment basically allows that cell to resist a high osmotic pressure. Now, what we want to focus on in this lecture is the structure of penicillin and the actual mechanism by which penicillin acts on that bacterial enzyme. So let's begin with the structure of penicillin. So penicillin consists of three important components. Component number one is the five membered ring we call thiozolidine. So thiozolidine consists of this five member ring here.