Bacteria have a peptidoglycan cell wall, which they are constantly restructuring as they expand and replicate. Penicillin (like other beta-lactam antibiotics) functions by disrupting the formation of peptidoglycan cross-links in the cellular wall of a given bacterium. Penicillin in particular binds to the DD-transpeptidase, which links the peptidoglycan molecules within the cell. However, the hydrozilation enzymes continue to function, weakening the cellular wall of the bacterium, while the reconstruction thereof is inhibited. Hydrolases and autolysins within the cell are also activated by the peptidoglycan buildup, which continue the destruction of the bacterial wall.