The three steps of tranlsation are initiation, elongation, and termination.
Initiation-- An mRNA joins to the small ribosomal unit at the 5' end region that has not been translated yet. The large ribosomal subunit attaches to the small subunit so that the firat codon is in line with the P building site. A tRNA that is carrrying the amino acid methionine attaches to the start codon (AUG) on the mRNA, which initiates elongation.
Elongation-- Attachment of first amino acid carries tRNA to A binding site. A tRNA and its amino acid attaches to the same A binding site. A peptide bond forms between the methionine and the amino acid carried at the A building site. Ribosome now moves towards in the 3' direction down the mRNA by three bases, or by one codon shifting the tRNA and polypeptide chain to the P binding site.
tRNA is then ejected from the E building region.
Elongation repeats until a stop codon is encountered.
Termination-- The polypeptide chain is now at the P site, and the stop codon is at the A site. A protein attaches to the stop codon at the A building site. This protein initiates separation in the polypeptide chain, which then goes into the cytoplasm.
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