<P> The covalent attachment to the tRNA 3 ' end is catalyzed by enzymes called aminoacyl tRNA synthetases . During protein synthesis , tRNAs with attached amino acids are delivered to the ribosome by proteins called elongation factors , which aid in association of the tRNA with the ribosome , synthesis of the new polypeptide and translocation ( movement ) of the ribosome along the mRNA . If the tRNA 's anticodon matches the mRNA , another tRNA already bound to the ribosome transfers the growing polypeptide chain from its 3 ' end to the amino acid attached to the 3 ' end of the newly delivered tRNA , a reaction catalyzed by the ribosome . </P>
which cellular component controls the correct attachment of amino acid to certain trna
aminoacyl tRNA synthetases