Penicillin interferes with the synthesis of peptidoglycan; it binds to proteins involved in cell wall synthesis (penicillin-binding proteins). This prevents the cross-linking of adjacent glycan chains. Lysozyme destroys existing bonds in the glycan chain; it breaks the bond that links the alternating N-acetylglucosamine and N-acetylmuramic acid molecules. Both penicillin and lysozyme result in a weakened cell wall, ultimately causing the cell to lyse. However, penicillin works only on actively growing cells, while lysozyme can cause lysis of both growing and nongrowing cells.