How do antibiotics work?

• A. They kill existing bacteria by disintegrating their cell walls
• B. Some antibiotics kill existing bacteria by causing the cell wall to disintegrate
• C. They disrupt viral replication
• D. They have no effect on bacteria

Answer: (B)

Antibiotics can kill bacteria by targeting structures or processes that are specific to bacteria. The statement that best matches how some antibiotics work is that some antibiotics kill existing bacteria by causing the cell wall to disintegrate. When a drug weakens the cell wall, the bacterium can’t maintain its shape or protect itself as it grows. As a result, osmotic pressure causes the weakened cell to burst, leading to death of the bacterium. This describes a real mechanism used by drugs like penicillins, which disrupt the enzymes that build the cell wall and thereby compromise its integrity.

This option is the best because it accurately reflects that this is true for some antibiotics, not all. A would imply that every antibiotic disintegrates cell walls, which isn’t accurate since many antibiotics work by other means (like inhibiting protein synthesis or DNA replication). The idea that antibiotics disrupt viral replication is incorrect because antibiotics target bacteria, not viruses. And saying they have no effect on bacteria is clearly false.