Antibiotics interfere with prokaryotic cell functions. Streptomycin is an antibiotic that interferes with the proper binding of tRNA to mRNA in prokaryotic ribosomes. Which of the following best predicts the most direct effect of exposing prokaryotic cells to streptomycin? A. Amino acid synthesis will be inhibited.
B. No mRNA will be transcribed from DNA
C. Posttranslational modifications will be prevented.
D. Synthesis of polypeptides will be inhibited.

The correct answer is D. Synthesis of polypeptides will be inhibited.

Explanation:

Streptomycin is an aminoglycoside antibiotic. Aminoglycosides are actively transported across the bacterial membrane, irreversibly bind to one or more receptor proteins specific to the 30S subunit of bacterial ribosomes, and interfere with the initiation complex between messenger RNA and the 30S subunit. DNA can be misread, leading to the production of non-functional proteins; polyribosomes separate and are unable to synthesize proteins. This results in accelerated transport of aminoglycosides, thereby increasing the breakdown of the cytoplasmic membranes of the bacteria and consequent cell death. Streptomycin specifically binds and inhibits the ribosomes of bacteria because the ribosomes of prokaryotic cells are not the same as those of eukaryotic cells. Specifically, it blocks the normal activity of the initiation complex, thereby halting protein synthesis and, on the other, it causes the incorporation of other amino acid different than the one encoded.

D. Synthesis of polypeptides will be inhibited.