Microbiology: A Systems Approach 4th Edition by Marjorie Kelly Cowan

Exercise 25

Figure 12.5. Where could penicillinase affect each of these antibiotics
Figure 12.5: Chemical structure of penicillins. All penicillins contain a thiazolidine ring (yellow) and a beta-lactam ring (red), but each differs in the nature of the side chain (R group), which is also responsible for differences in biological activity.