Final answer:
Peptidyl transferase catalyzes peptide bond formation in the elongation phase of translation. Kinetic proofreading happens in both initiation and elongation. In E. coli, EF-Tu delivers an aminoacyl-tRNA during elongation.
Step-by-step explanation:
In translation, peptidyl transferase catalyzes peptide bond formation, which is responsible for joining amino acids in the growing polypeptide chain. This process occurs in the elongation phase of translation. Kinetic proofreading, on the other hand, is a step during tRNA selection that occurs in both initiation and elongation. In E. coli, EF-Tu delivers an aminoacyl-tRNA to the ribosome during the elongation phase of translation.