K which is involved in the lysis of collagen. Through the action of carbonic anhydrase, osteoclasts release hydrogen ions. This allows the dissolution of the bone matrix.

6. C – They inhibit DNA gyrase Quinolones inhibit DNA gyrase (also known as DNA topoisomerase II, an enzyme required in DNA unwinding). Trimethoprim and methotrexate inhibit dihydrofolate reductase. Sulphonamides inhibit dihydropteroate synthetase. Rifampicin inhibits RNA polymerase. 5-Nitroimidazoles (such as metronidazole) inhibit DNA synthesis by reducing a nitro group and forming reactive intermediates.