How do aldehydes achieve sterilisation?

• A. Disrupting cell membranes
• B. Inactivating cell proteins
• C. Damaging DNA
• D. Producing free radicals

Answer: (B)

Aldehydes sterilise by chemically inactivating microbial proteins through alkylation and cross-linking. They react with nucleophilic sites on proteins—especially amino groups—forming covalent bonds that denature enzymes and structural proteins. This disrupts essential cellular functions, metabolism, and integrity, leading to cell death. While cross-linking can also affect nucleic acids, the key effect behind their sterilising power is the loss of protein function, which shuts down vital processes across many organisms when given adequate contact time. They don’t rely on disrupting membranes or generating free radicals, which is why other mechanisms like membrane damage or radical production don’t describe their action.