Question

During protein synthesis, formation of peptide bonds take place between

• A. -NH${}_2$ group of 'P' site amino acid and -COOH group of 'A' site amino acid
• B. -COOH group of 'P' site amino acid and -NH${}_2$ group of 'A' site amino acid
• C. > C= 0 group of 'P' site amino acid and -NH${}_2$ group of 'A' site amino acid.
• D. None of the above

Answer 1

The correct option is B -COOH group of 'P' site amino acid and -NH${}_2$ group of 'A' site amino acid

During translation, a small ribosomal subunit attaches to an mRNA molecule. At the same time, an initiator tRNA molecule recognizes and binds to a specific codon sequence on the same mRNA molecule. A large ribosomal subunit then joins the newly formed complex. The initiator tRNA resides in one binding site of the ribosome called the P site, leaving the second binding site, the A site, open. When a new tRNA, molecule recognizes the next codon sequence on the mRNA, it attaches to the open A site. A peptide bond forms connecting the amino acid of the tRNA in the P site to the amino acid of the tRNA in the A binding site. The Formation of peptide bonds take place between -COOH group of 'P' site amino acid and NH${}_2$ group of 'A' site amino acid. As the ribosome moves along the mRNA molecule, the tRNA in the P site is released and the tRNA in the A site is translocated to the P site. The A binding site becomes vacant again until another tRNA that recognizes the new mRNA codon takes the open position. Thus, the correct answer is option B.