Where is the amino acid binding site located on tRNA?

• A. CCA end
• B. Anticodon end
• C. Phosphate backbone
• D. D-loop

Answer: (A)

The amino acid is attached to the 3' end of the tRNA, specifically the CCA tail. The aminoacyl-tRNA synthetase covalently links the amino acid to the 3'-OH of the terminal adenosine (A76) in that CCA sequence, forming an ester bond. This location is what “charges” the tRNA for incorporation into a growing polypeptide.

The anticodon end is the region that base-pairs with the mRNA codon, so it’s not where the amino acid attaches. The phosphate backbone is the sugar-phosphate framework of the molecule, not a reactive site for amino acid attachment. The D-loop is a structural loop involved in tRNA folding and recognition, but again not the binding site for the amino acid.