Why a Cell Dies When Exposed to Penicillin
Penicillin kills bacterial cells by interfering with cell wall synthesis. The drug inhibits enzymes needed to build peptidoglycan, the rigid mesh that maintains bacterial shape and protects against osmotic pressure.
How Penicillin Triggers Cell Death
Without a stable cell wall, the bacterium cannot withstand internal osmotic pressure. Water enters the cell, causing it to swell and eventually lyse. This process is called osmotic lysis and is the primary reason the cell dies in the presence of penicillin.
Why Human Cells Are Not Affected
Human cells lack a rigid peptidoglycan cell wall, so penicillin does not target them in the same way. The drug specifically disrupts bacterial wall formation, which is why it selectively kills bacteria while sparing most human cells.
For more on antibiotic mechanisms, see NCBI Bookshelf.
