Question

List two essential roles of ribosome during translation. (NCERT)

Answer 1

Ans. The essential roles of ribosome during translation are as follow-

1. Ribosomes act as the physical site of translation of mRNA into proteins.

2. The large subunits of a functional ribosomes catalyze the formation of peptide bond between two amino acids, thus also act as peptidyl transferase enzyme. The catalytic activity of the ribosomes is due to presence rRNA (23S rRNA of prokaryotic 50S subunit, 28S rRNA of eukaryotic 60S subunit) in the larger subunit.

3. The smaller subunit (say, 16s rRNA in 30S subunit in bacteria) binds to the mRNA in 5’-3’direction and helps aligning the mRNA in correct orientation for translation to occur. Since the codons on mRNA are read only in 5’-3’ direction, any change in polarity of mRNA bound to ribosomes would yield unexpected outcomes during translation.

4. Ribosomes also ensure that translation starts exactly at the translation start site on mRNA (mostly, AUG codon). Since change in translation start site even by a single base would yield undesirable outcomes, this process always ensure the formation of correct protein through translation.