Question

write one biochemical pathway in bacteria that is blocked by the antibiotics like penicillin

Answer 1

Antibiotics such as penicillin binds to the protein that are responsible for the synthesis wall in bacteria.By binding specific  protein of bacteria penicillin blocks the biochemical pathway of cell wall synthesis in bacteria.Antibiotics also blocks DNA synthesis,protein synthesis and ultimately results in cell death.

Answer 2

Antibiotics prevent and destroy the biochemical ways that the bacteria use to build cell wall for themselves.  So they do not multiply any more and slowly get destroyed ie., die.