Chloramphenicol is an antibiotic that targets prokaryotic (70s) ribosomes, but not eukaryotic (80s) ribosomes. which of these questions stems from this observation, plus an understanding of eukaryotic origins?
a) can chloramphenicol also be used to control human diseases that are caused by archaeans? b) can chloramphenicol pass through the capsules possessed by many cyanobacteria? c) if chloramphenicol inhibits prokaryotic ribosomes, should it not also inhibit mitochondrial ribosomes? d) why aren't prokaryotic ribosomes identical to eukaryotic ribosomes? e) how is translation affected in ribosomes that are targeted by chloramphenicol?

A) Yes, chloramphenicol can also be used to control human diseases that are caused by archaeans.

B) Yes, chloramphenicol can pass through the capsules possessed by many cyanobacteria.

C) Yes, chloramphenicol should also inhibit mitochondrial ribosomes.

D) Prokaryotic ribosomes are not identical to eukaryotic ribosomes because they are made up of 50S and 30S subunits while eukaryotic ribosomes are made up of 60S and 40S subunits.

E) Chloramphenicol blocks peptide bond formation by inhibiting activity of enzyme known as peptidyl transferase.

Explanation:

A) Just like prokaryotes, archaeans too have 70S ribosome that is why chloramphenicol can block translation in some archaeans too.

B) Chloramphenicol passes through capsules possessed by cyanobacteria either by passive diffusion or facilitated diffusion.

C) Since chloramphenicol targets 70S ribosomes and mitochondria too have 70S ribosomes just like prokaryotes that is why this antibiotic should also inhibit mitochondria.

D) Prokaryotes have 70S ribosome which is made up of 50S and 30S subunits while eukaryotic ribosomes are 80S which are made up of 60S and 40S subunits. Its because of this difference, the protein residues that participate in peptide bond formation are different in prokaryotes and eukaryotes.

E) In prokaryotes, chloramphenicol blocks translation elongation by inhibiting peptidyl transferase activity. This enzyme typically binds 23S rRNA at A2451 & A2452 residues thereby preventing peptide bond formation. It may be noted that 23S rRNA is a part of 50S rRNA.

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