Beta-lactam antibiotics work by inhibiting cell wall formation in the bacterial organism and are the most widely used group of antibiotics. Imagine a wall being incomplete when the cell reproduces
Beta-lactams have in common is a beta-lactam ring in their structure
Gram negative bacteria is less thick
Gram positive bacteria have a thicker cell wall Focus on the letter P for penicillin and protection. Penicillin targets the cell wall. A wall Protects 
DNA contains genetic information 
Bactericidal kills bacteria 
Bacteriostatic stops reproduction of bacteria
Thick wall protects more 
Penicillin comes from mold 
Gram negative bacteria more common in GI tract
Gram positive bacteria more common in respiratory tract Imagine a cross on a chest 