Final answer:
During protein synthesis, charged aminoacyl-tRNA enters the ribosome's A site and forms a peptide bond with the growing polypeptide chain in the P site, followed by translocation. ATP and GTP are required for tRNA activation and ribosomal translocation, which are highly efficient processes catalyzed by various enzymes and elongation factors.
Step-by-step explanation:
The process of protein synthesis involves several steps, including initiation, elongation, and termination. During the elongation phase of protein synthesis, aminoacyl-tRNA molecules sequentially enter and exit the ribosome. The amino acid attached to the tRNA in the A site (Aminoacyl site) forms a peptide bond with the growing chain held by the tRNA in the P site (Peptidyl site). This is followed by a translocation event where the ribosome advances three nucleotides along the mRNA, shifting the peptidyl-tRNA from the A to the P site.
Activation of tRNA, an important part of the translational process, involves the enzymatic addition of an amino acid to the tRNA molecule. This charging of the tRNA, also referred to as aminoacylation, requires ATP and an enzyme called aminoacyl-tRNA synthetase. The charged aminoacyl-tRNA then enters the A site of the ribosome, and its anticodon pairs with the corresponding codon on the mRNA. Following peptide bond formation, the now uncharged tRNA exits through the E site (Exit site).
Each elongation cycle, catalyzed by peptidyl transferase, consumes energy equivalent to one ATP for tRNA activation and two GTPs for translocation and elongation factor activities. Remarkably, a bacterial ribosome can add amino acids to a growing polypeptide chain at the rate of about 20 per second, highlighting the efficiency of this cellular machinery.