Final answer:
During protein elongation, the next aminoacyl-tRNA enters the ribosome at the A site based on codon-anticodon interaction. Elongation factors hydrolyze GTP to provide the energy for each step. Peptide bonds form between the amino acid attached to the A-site tRNA and the amino acid attached to the P-site tRNA, catalyzed by peptidyl transferase.
Step-by-step explanation:
The first step in elongation is the entry of the next aminoacyl-tRNA (aa2- tRNAaa2), which requires the free energy of GTP hydrolysis. The energy is supplied by the hydrolysis of GTP bound elongation factor 2 (EF2-GTP). The aa2-tRNAaa2 enters the ribosome based on codon-anticodon interaction at the A site.
Elongation proceeds with charged tRNAs sequentially entering and leaving the ribosome as each new amino acid is added to the polypeptide chain. Movement of a tRNA from A to P to E site is induced by conformational changes that advance the ribosome by three bases in the 3' direction. The energy for each step along the ribosome is donated by elongation factors that hydrolyze GTP. Peptide bonds form between the amino group of the amino acid attached to the A-site tRNA and the carboxyl group of the amino acid attached to the P-site tRNA. The formation of each peptide bond is catalyzed by peptidyl transferase, an RNA-based enzyme that is integrated into the 50S ribosomal subunit. The energy for each peptide bond formation is derived from the high-energy bond linking each amino acid to its tRNA.
After peptide bond formation, the A-site tRNA that now holds the growing peptide chain moves to the P site, and the P-site tRNA that is now empty moves to the E site and is expelled from the ribosome. GTP is cleaved to form GDP, and the EF-Tu-GDP complex is released. EF-Ts regenerates EF-Tu-GDP to EF-Tu-GTP.