Q.Ribosomes are composed of two subunits; the smaller subunit of a ribosome has a binding site for _________ and the larger subunit has two binding sites for two __________.

Translation decodes an mRNA's codon sequence into a polypeptide's amino acid sequence at the ribosome, a two-subunit, non-membranous ribonucleoprotein machine with one mRNA-binding site and two tRNA-binding sites: the P-site (peptidyl-tRNA, holding the tRNA attached to the growing chain) and the A-site (aminoacyl-tRNA, receiving each new charged tRNA, where codon-anticodon pairing by hydrogen bonds actually occurs). Translation has three stages: initiation, beginning at the AUG start codon (coding for methionine), with the initiator tRNA occupying the P-site; elongation, in which an incoming aminoacyl-tRNA pairs with the mRNA codon in the A-site, a peptide bond forms (catalysed by the ribosome's own peptidyl-transferase, a ribozyme activity) between the P-site and A-site amino acids, and the ribosome then translocates one codon further along the mRNA (a GTP-hydrolysis-dependent step), shifting the peptidyl-tRNA into the now-empty P-site and freeing the A-site for the next tRNA; and termination, when a stop codon (UAA, UAG or UGA) enters the A-site and a release factor binds instead of a tRNA, releasing the finish …