Final answer:
GTP hydrolysis during the first step of elongation allows the next aminoacyl-tRNA to enter the ribosome's A site, enables GDP dissociation from EF2 and GDP rephosphorylation by EF3, facilitating the translocation of tRNAs from the A to P to E site and allowing the continuation of the translation process.
Step-by-step explanation:
In the first step of elongation, once the GTP is hydrolyzed, several events occur. The energy from GTP hydrolysis, which involves elongation factor 2 (EF2-GTP), allows the next aminoacyl-tRNA (aa2-tRNAaa2) to enter the A site of the ribosome based on codon-anticodon interaction.
The GDP formed from hydrolysis then dissociates from EF2, and elongation factor (EF3) rephosphorylates GDP back to GTP. This cycle of GTP hydrolysis and rephosphorylation enables the ribosome to continue protein synthesis by allowing new charged tRNAs to enter the ribosome and the formation of peptide bonds.
The continuation of this process facilitates the ribosome to shift three bases in the 3' direction, moving a tRNA from A to P to E site. This translocation step requires the hydrolysis of GTP catalyzed by another elongation factor, signifying the importance of GTP in the translation process. As the elongation cycles repeat, each amino acid addition to the polypeptide chain not only consumes ATP for tRNA charging but also requires the hydrolysis of two GTPs, thus underlining the cost-intensive nature of protein synthesis in cellular activities.