Answer:
(Iv) A small ribosomal subunit binds with mRNA
i) The anticodon of tRNA base pairs with the mRNA codon at the A site
ii) Peptide bond formation between amino group of amino acid in A site and the carboxyl end of the polypeptide in the P site
(III) Translocation of tRNA from the A site to the P site
Explanation:
Translation is the second process involved in the same of protein. It occurs in the ribosome. Translation begins when the ribosome attaches itself to the mRNA molecule in the cytoplasm using small ribosomal subunits. This allows the tRNA (transfer RNA) to bind to the start codon of the mRNA for translation to be initiated.
The tRNA uses its anticodon, which is complementary to the mRNA codon, to bind to the mRNA coding in the A-site of the RIBOSOME. The tRNA then carries the amino acid that corresponds the codon it reads. This leaves the mRNA codon exposed in the other site of the ribosome, which is bind to by another tRNA anticodon.
The tRNA then carries another amino acid that corresponds the codon it reads in the other site. After this, the first tRNA transfers its amino acid to the amino acid in the newly arrived tRNA which forms a peptide bond between the amino group of amino acid in A site and the carboxyl end of the polypeptide in the P site.
After this peptide bond formation, the ribosome uses a ratcheting mechanism to advance the mRNA, three nucleotides at a time. The ribosome also shifts the tRNA carrying the polypeptide chain into its recently vacated site (P site). This process is called TRANSLOCATION.
