Enzymes which are specific to different tRNA types catalyse the bonding of amino acids to tRNA molecules, which requires ATP for energy.
There are 4 stages to translation: initiation, elongation, translocation and termination.
During initiation, the small ribosomal subunit binds to the 5' end of mRNA and moves along it until it reaches the start codon (which is AUG). Then the tRNA molecule binds to the codon (via its anticodon), due to complementary base pairing (A-T, C-G). After, the large ribosomal subunit binds at the P-site of tRNA, forming a complex.
During elongation, a second tRNA molecule pairs with the next codon at the ribosomal A-site and the amino acid is covalently bonded to the amino acid at the P-site.
During translocation, the ribsome moves along to the next codon, and the first tRNA molecule is moved to the E-site and is released. So, a new tRNA molecule enters the now empty A site and the process is repeated, synthesising a polypeptide chain in a 5'-3' direction.
(If multiple ribsomes act on the same chain they form a polysome)
Finally, termination occurs when the stop codon is reached. This is a codon that does not code for any amino acid. The polypeptide chain is released and the ribosome disassembles to be used again for another chain.
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