During translation, which bond formation is directly responsible for linking amino acids into a growing polypeptide chain?

• A. Peptide bond formation between adjacent amino acids.
• B. Phosphodiester bond formation in the mRNA.
• C. Glycosidic bond formation in sugar units.
• D. Hydrogen bonding between codon and anticodon.

Answer: (A)

The key concept is that the growing protein chain is lengthened by peptide bonds. During translation, the ribosome catalyzes the formation of a peptide bond between the carboxyl end of the existing polypeptide (tethered to the tRNA in the P site) and the amino group of the new amino acid on the tRNA in the A site. This peptidyl transferase reaction, a dehydration synthesis, is what directly links adjacent amino acids and extends the polypeptide chain. The other bonds mentioned serve different roles: phosphodiester bonds link nucleotides in mRNA, glycosidic bonds connect sugar units, and hydrogen bonds between codon and anticodon help position tRNA but do not join amino acids.