Question

Protein synthesis takes place much more slowly in eukaryotes than in prokaryotes. Which of the following is a reason that this is true?

(a) The formation of a peptide bond in prokaryotic ribosomes occurs nearly twice as fast as in eukaryotic ribosomes.

(b) Prokaryotes have higher concentrations of charged tRNAs than eukaryotes do.

(c) Eukaryote cells are, on average, much larger than prokaryote cells.

(d) Eukaryotic mRNA must be synthesized in the nucleus and exported to the cytosol where protein translation occurs.

Answer 1

Ribosomes. Eukaryotic ribosomes are larger. They consist of a 60S large subunit and a 40S small subunit, which come together to form an 80S particle having a mass of 4200 kd, compared with 2700 kd for the prokaryotic 70S ribosome. The 40S subunit contains an 18S RNA that is homologous to the prokaryotic 16S RNA. The 60S subunit contains three RNAs: the 5S and 28S RNAs are the counterparts of the prokaryotic 5S and 23S molecules; its 5.8S RNA is unique to eukaryotes.

Answer is (a)