Elongation of the polypeptide now occurs, with amino acids being added one by one. The codon in the A site of the ribosome pairs with the anticodon of the appropriate tRNA molecule. Part of the ribosome catalyzes the formation of a peptide bond between the amino acid extending from the P site and the amino acid extending from the A site. The tRNA in the A site now translocates to the P site. The tRNA that was in the P site moves to the E site and exits from the ribosome. Meanwhile, a new tRNA brings its amino acid to the A site and the process is repeated.