How do antibiotics (say Penicillin) work on bacteria but not on human beings

How do antibiotics (say Penicillin) work on bacteria but not on human beings? 

Define antibiotic And Explain how it

i s able to control bacterial infections but not viral infections. 

Answer:  Antibiotics (anti means against, biotic - living) are types of medications that destroy or slow the growth of bacteria. 

They are often termed as antibacterials. They work against the life processes

of bacteria. They commonly block biochemical pathways important for bacteria. Many bacteria, for example, make a cell-wall to protect themselves. 

The antibiotic penicillin blocks the bacterial processes that build the cell wall. Thus bacteria fail to build their cell-wall, stop multiplying and die out.

Human cells don’t make a cell-wall anyway, so penicillin cannot have such an effect on us.