Moist heat kills microorganisms by Multiple Choice O destruction of carbohydrates in the cell wall. O destruction of the nuclear envelope. denaturation of nucleic acids. O O dissolving the capsule. irreversible denaturation of proteins. O
The Correct Answer and Explanation is:
Correct Answer: ✅ Irreversible denaturation of proteins
Explanation
Moist heat is a highly effective method for killing microorganisms and is commonly used in sterilization processes, especially in medical and laboratory settings. The primary mechanism by which moist heat kills microorganisms is through irreversible denaturation of proteins. Proteins are essential for the structural integrity and metabolic functions of microbial cells. When exposed to high temperatures in the presence of moisture (such as steam), the hydrogen bonds and other interactions that maintain a protein’s structure are disrupted. This leads to denaturation, a process where the protein loses its three-dimensional shape and, consequently, its function.
Moist heat methods include boiling, pasteurization, and autoclaving. Among these, autoclaving is the most effective and is considered the gold standard for sterilization. It uses pressurized steam at temperatures of 121°C or higher for specific durations to ensure complete destruction of all forms of microbial life, including resistant bacterial spores.
Unlike dry heat, which also kills by denaturing proteins and oxidizing cellular components, moist heat is more efficient because water conducts heat better than air, allowing for faster and more uniform heat penetration into cells. This increased efficiency makes it possible to sterilize materials at lower temperatures and in less time compared to dry heat.
The other options in the question are incorrect:
- Destruction of carbohydrates in the cell wall and dissolving the capsule may weaken a microorganism but are not primary lethal mechanisms.
- Destruction of the nuclear envelope applies to eukaryotic cells, not most microorganisms (many are prokaryotic and lack a nuclear envelope).
- Denaturation of nucleic acids can occur at very high temperatures but is secondary to protein denaturation.
In summary, moist heat sterilization works mainly by irreversibly denaturing microbial proteins, effectively killing cells and ensuring sterility.
