Despite the more complex initiation factors

Despite the more complex initiation factors loading the small ribosomal subunit
, protein synthesis in prokaryotes and eukaryotes is quite similar. The ribosomal subunits are odd numbers 30S and 50S in prokaryotes and even
numbers 40S and 60S in eukaryotes. At the start of translation, initiation factors, mRNA, and initiation aminoacyl-tRNA bind to the dissociated small ribosomal
subunit (answers a, c-e thus incorrect). Only after the small ribosomal subunit is primed with mRNA and initiation aminoacyl-tRNA does the large ribosomal subunit bind to it. Once this happens, elongation factors bring the first aminoacyl-tRNA of the nascent protein to the A site. This is the step inhibited by tetracycline. Then, peptidyl transferase forges a peptide bond between the initiation amino acid and the first amino acid of the forming peptide. The now uncharged initiation tRNA
leaves the P site, and the peptidyl-tRNA from the A site moves to the now vacant P site with the two amino acids attached. The ribosome advances three bases to
read the next codon, and the process repeats. Macrolide antibiotics (eg, azithromycin, Zithromax, and erythromycin) bind to the bacterial 50S ribosome and inhibit this
translocation step. When the stop signal is reached after the complete polypeptide has been synthesized, releasing factors bind to the stop signal, causing peptidyl transferase to hydrolyze the bond that joins the polypeptide at the A site to the tRNA. Factors prevent the reassociation of ribosomal subunits in the absence of new
initiation complex.