Question

Why do antibiotics kill bacteria, but not viruses?
A) Antibiotics stimulate the immune system against bacteria, but not viruses
B) Viruses have ways of blocking antibiotics
C) Viruses are too small to be affected by antibiotics
D) viruses do not have a metabolism

Answer 1

Hint:Viruses are inert particles that have different mechanisms by which host cells take them in. Once in, viral DNA inserts into the host DNA making it impossible for the body to recognise and destroy the infectious agent.

Complete answer:
Bacteria, unless in the spore stage, are metabolically active organisms. They are continuously using their machinery, specifically DNA, RNA and ribosomes, and structurally components like the cell wall to function. Antibiotics are designed specifically to target these metabolic activities. There are some antibiotics that prevent ribosomal formation, that block DNA replication, and that damage the bacterial cell wall.

Antibiotics therefore act directly on the bacterial cells, and not by stimulating the host immune system. Option A is incorrect.

Viruses themselves do not have any means of blocking the activity of antibiotics. Because they are metabolically inert, they are not affected by any antiviral drugs. The only drugs that may work would be those that prevent uptake of the virus by the host cells.

Viruses are not too small to be affected by antibiotics. An antibiotic is a molecule, not a cell, which enters the living cell to interfere with its machinery. Option C is incorrect.

Antibiotics are designed to target specific metabolic and biochemical processes. As viruses are metabolically inert, requiring the machinery of the host cell to function and reproduce, they are not affected by antibiotics.

Hence the correct answer is option D

Note:Even though viruses are not targeted by antibiotics, we are still prescribed certain antibiotics when suffering from a viral infection. This is because our weakened states may make us more susceptible to a secondary bacterial infection.