Question

Which one of the following antibiotics kills the bacterial cell by inhibiting the polymerisation of peptidoglycan?
A) Aminoglycosides
B) Fluoroquinolones
C) Quinines
D) Penicillins

Answer 1

Hint:There were no effective therapies for infections caused by bacteria before the 20th century, including pneumonia , tuberculosis, gonorrhoea, rheumatic fever and urinary tract infections. Antibiotics must selectively target bacteria for eradication and not the cells of their human host to be successful in the treatment of human infections.

Complete Answer:
There are a variety of different types of antibiotics. They may have entirely different bacterial targets, or they may function on the same target but at a different location. In general, there are three major antibiotic targets in bacteria:
1. Cell wall or membranes that surround the bacterial cell
2. Machinery producing DNA and RNA nucleic acids
3. Machinery processing proteins (ribosomes and related proteins)
Most bacteria create a cell wall consisting mainly of a macromolecule called peptidoglycan, made up of amino sugars and short peptides.Human cells do not produce peptidoglycan or require it. In the assembly of this macromolecule, penicillin, one of the first antibiotics to be widely used, prevents the final cross-linking step, or transpeptidation.A very weak cell wall that breaks, destroying the bacterium, is the result.There is no risk to the human host because penicillin does not hinder any metabolic process that is taking place inside us.Bacteria can also be selectively eliminated by targeting their metabolic pathways.Sulfonamides, such as sulfamethoxazole, are similar in structure to para-aminobenzoic acid, a compound essential for folic acid synthesis. All cells need folic acid and can easily spread to human cells. But the vitamin can't reach the bacterial cells, so the bacteria have to make their own.

Thus the correct answer is option(D) Penicillin.

Note:Many other compounds are capable of killing both bacterial and human cells. It is the selective action of antibiotics against bacteria that makes them effective in the treatment of infections while at the same time allowing the host to live another day.