Final answer:
A peptide bond holds amino acids together in a polypeptide chain during the elongation phase of translation, and these bonds form at the ribosome's A site, facilitated by peptidyl transferase and powered by GTP hydrolysis.
Step-by-step explanation:
A peptide bond holds the amino acids of a growing polypeptide chain together as they elongate from the ribosome's A site during translation. During the elongation phase of translation, peptidyl transferase, an RNA-based enzyme within the 50S ribosomal subunit, catalyzes the formation of peptide bonds.
This process involves the amino group of an amino acid attached to the A-site tRNA reacting with the carboxyl group of the amino acid linked to the P-site tRNA. As the peptide bond forms, the growing polypeptide chain attached to the A-site tRNA moves to the P site, allowing for a new tRNA carrying an amino acid to bind to the now vacant A site. This repetitive cycle, powered by GTP hydrolysis and facilitated by elongation factors, extends the polypeptide chain with remarkable efficiency, with the bacterial translation machinery capable of adding amino acids at a rate of 0.05 seconds per addition.