Final answer:
Each aminoacyl-tRNA synthetase specifically attaches the amino acid to a tRNA molecule according to the tRNA's anticodon, ensuring the proper incorporation of amino acids into the polypeptide chain during protein synthesis.
Step-by-step explanation:
Each aminoacyl-tRNA synthetase recognizes and attaches a specific amino acid to a tRNA molecule based on the anticodon of the tRNA. This process, often referred to as tRNA "charging," ensures that the tRNA molecule is linked to its correct or cognate amino acid. The specificity is dictated by the tRNA's structure and its unique anticodon, a sequence of three nucleotides that is complementary to the corresponding codon on mRNA.
For instance, if the mRNA codon is GCA, it will pair with the tRNA anticodon UGC, which carries the amino acid alanine. The tRNA is charged by the corresponding aminoacyl-tRNA synthetase, which catalyzes the bond between the amino acid and tRNA, making use of ATP to activate the amino acid before transferring it to the tRNA. As a result, an amino acid is correctly added to the polypeptide chain during protein synthesis, based on the mRNA code. The enzyme ensures strict pairing by binding to both the specific tRNA and its corresponding amino acid.