Question

Penicillin inhibits the growth of bacteria. It's site of action is

• A. Mesosome
• B. Ribosome
• C. Genophore
• D. Episome
• E. Cell wall

Answer 1

The correct option is E Cell wall

The cell walls of bacteria are composed of a macromolecule peptidoglycan which is a repeating framework of long glycan chains having alternate N-acetyl glucosamine and N-acetyl muramic acid; these glycan chains are cross-linked by short peptide fragments to provide a strong but flexible support framework. Penicillin target the peptide cross-links in the peptidoglycan and disrupt the cell wall integrity. Exposure of penicillin to bacteria make them loose their cell wall completely and become protoplast (a fragile cell bounded only by a membrane) which is highly susceptible to lysis. This makes option E correct. Mesosome is an extension of the cell membrane presence in cytoplasm as infolding and serves to increases surface area. Ribosomes are the site for protein synthesis and have two subunit; large and small. Prokaryotic ribosomes have 30S and 50S subunits that together make a 70S ribosome. DNA of a prokaryote is termed as genophore that serve to inherit genetic information from generation to generation. The plasmids with ability to integrate themselves in cellular chromosomes are termed as episomes. Mesosomes, ribosomes, genophore, episomes do not have peptide cross links and thus, are not affected by penicillin. Thus, the correct answer is option E.