Final answer:
During translation elongation, the charged tRNA enters the ribosome at the A site and after peptide bond formation, it moves to the P site, and subsequently to the E site before exiting.
Step-by-step explanation:
During the elongation stage of translation, the entry of the charged transfer RNA (tRNA) occurs at the A site of the ribosome. Initially, the tRNA carrying the methionine amino acid binds to the P site during the initiation phase. However, as elongation proceeds, new charged tRNAs enter the ribosome at the A site. Each tRNA enters based on the complementarity of its anticodon to the mRNA codon located at the A site. This is a critical step for the addition of new amino acids to the growing polypeptide chain.
Once the charged tRNA has delivered its amino acid, it is translocated to the P site where a peptide bond forms between the newly arrived amino acid and the existing chain. The tRNA that was previously in the P site now moves to the E site to exit the ribosome after transferring its polypeptide to the tRNA in the A site. This cyclical process continues with each codon being translated until a stop codon is reached, signaling the termination of translation. The elongation process in protein synthesis is a complex mechanism powered by GTP hydrolysis and facilitated by various elongation factors.