Here's a breakdown of the process:
1. Initiation: The ribosome assembles on the mRNA, and the first tRNA carrying the amino acid methionine binds to the start codon.
2. Elongation:
* Codon recognition: A second tRNA carrying its corresponding amino acid recognizes the next codon in the mRNA sequence.
* Peptide bond formation: The amino acid attached to the first tRNA is transferred to the amino acid on the second tRNA, forming a peptide bond.
* Translocation: The ribosome moves one codon down the mRNA, shifting the first tRNA (now empty) to the exit site and the second tRNA (carrying the growing polypeptide chain) to the peptidyl site. The empty tRNA is released, and the process repeats.
3. Termination: The ribosome encounters a stop codon, causing the release of the polypeptide chain and the disassembly of the ribosome.
Translocation is the crucial step where the two tRNAs are aligned, allowing the peptide bond to form between their attached amino acids. This process continues as the ribosome moves along the mRNA, building the polypeptide chain one amino acid at a time.