Question

Streptomycin inhibits protein synthesis on 70S ribosomes, cycloheximide inhibits protein
synthesis on 80S ribosomes. Therefore, what is true?
a. Both streptomycin and cycloheximide can be used as antibiotics
b. Only streptomycin can be used as an antibiotic
c. Only cycloheximide can de used as an antibiotic

Answer 1

Antibiotics :-
• This is the drug which is used to treat a bacterial infection or in other words it is used to kill bacteria.
• Bacteria is a prokaryotic type call so antibiotic drug should have a mechanism of action which kills prokaryotic cells.
In question,
• 70S type of ribosomes are found in prokaryotic or bacterial cells whereas 80S type of ribosomes are found in eukaryotic or animal cells.
• So, streptomycin which acts to 70S ribosome, can inhibit the bacterial growth and also has no effect on animal cells.
• Cycloheximide acts on 80S ribosome, so it has no effect on bacterial cells.
So, Only streptomycin can be used as antibiotic.

• Cycloheximide is used against fungal infections because fungal cells are eukaryotic cells.