Which set lists the tRNA binding sites on the ribosome?

• A. B, C and D
• B. A, B and C
• C. A, P and E
• D. P, E and F

Answer: (C)

In translation, the ribosome has three tRNA binding sites: A for aminoacyl-tRNA entry, P for peptidyl-tRNA holding the growing polypeptide, and E for the exit of spent tRNA. The cycle starts with a tRNA carrying the next amino acid entering at the A site, a peptide bond forms at the P site, and after translocation, the tRNA in the P site moves to the E site to exit while the tRNA in the A site shifts into the P site to continue elongation. The set that lists these sites is A, P and E. The other options include letters that don’t correspond to tRNA binding sites or omit a true site, so they aren’t correct.