Question

What is a ribosome cycle? Explain.

Answer 1

A single ribosome Cycle involves association of ribosomal subunits, protein synthesis (translation) and then the dissociation of the ribosomal subunits. The basic steps involved in ribosome cycle are:

1. The mRNA binding with the small ribosomal subunit: Then initiator tRNA carrying the first amino acid Methionine will bind at the AUG codon on P-site of the small subunit.

2. Association of small and large subunits of ribosome: The binding of initiator tRNA facilitates the assembly of small and large subunit.

3. Protein synthesis: The aminoacyl-tRNA corresponding to the mRNA codon will bind at the A site of the ribosome. The peptide bond will be formed between the first and second amino acid residues. Then the ribosome will translocate and move one codon forward resulting in vacant A site for next aminoacyl-tRNA molecule. This process continues until the ribosome encounter stop codon in the mRNA, then instead of tRNA molecule proteins called release factors will bind at the A site of the ribosome leading to the release of polypeptide chain.

4. Dissociation of small and large subunits of ribosome.

These steps constitute a single ribosome cycle and this process will be continued for the production of next protein.