Which ribosomal sites are used for tRNA binding during translation?

• A. Ribosome exit site
• B. Start site
• C. P and A site on Ribosomes
• D. E site

Answer: (C)

During translation, tRNA binding takes place at two ribosome sites: the aminoacyl (A) site and the peptidyl (P) site. The aminoacyl-tRNA carrying the next amino acid binds at the A site. The tRNA holding the growing peptide chain sits at the P site, where peptide bond formation occurs between the growing chain and the new amino acid. After the bond forms, the ribosome shifts so that the tRNAs move: the growing chain is now transferred to the A-site tRNA and the spent tRNA moves to the E site to exit. The E site is an exit path for tRNA, not a binding site for incoming tRNA. That’s why tRNA binding during translation involves the A and P sites.