How do penicillins work?
Penicillin antibiotics stop the spread of bacterial infection by disrupting the mechanism by which bacteria build their CELL WALL.
No cell wall= no bacteria as there is uncontrolled osmosis and swelling of the bacteria, destroying the internal cell environment.
If existing bacteria try to multiply then they have to build their cell wall. Since Penicillins act by damaging the cell walls of the bacteria when they are in the process of reproduction they can kill existing bacteria attempting to multiply.
The exact mechanism is by inhibiting the enzyme involved in cross linking the peptidoglycan layer of the cell wall. (Cell wall shown opposite)
Human cells do not have a cell wall.
So penicillins do not directly harm humans via their antibacterial action