Final answer:
During the elongation step of translation, the ribosome translocates, transferring a specific codon of mRNA between the A and P sites, enabling a charged tRNA to bind, form a peptide bond with the amino acid at the P site, and shift the tRNA from the P to the E site, where it is released.
Step-by-step explanation:
During the elongation step of translation, the ribosome translocates so that a specific codon of mRNA effectively transfers between the A and P sites. This translocation requires the aid of an elongation factor known as EF-G or translocase, and involves the movement of a charged tRNA. Initially, a charged tRNA binds to the A site of the ribosome. Following the formation of a peptide bond between the amino acids of the tRNA at the A site and the P site, the ribosome moves along the mRNA. Consequently, the tRNA that was in the A site now shifts to the P site, and the tRNA that was in the P site is moved to the E site, where it is released into the cytosol.
This process of translocation ensures that the ribosome progresses along the mRNA strand one codon at a time in the 5' to 3' direction, allowing for the synthesis of the polypeptide chain. The energy for this translocation and peptide bond formation is derived from GTP hydrolysis, facilitated by elongation factors.