Final answer:
The aminoacyl-tRNA synthetase determines the amino acid that is linked to a particular tRNA by catalyzing the attachment in a process called 'charging' the tRNA.
Step-by-step explanation:
The amino acid that is linked to a particular tRNA is determined by the aminoacyl-tRNA synthetase. These enzymes are specifically responsible for the process of "charging" the tRNA, which means they attach the correct amino acid to its appropriate tRNA. For each amino acid, there exists at least one aminoacyl-tRNA synthetase. The anticodon of a tRNA is crucial as well because it pairs with a complementary codon on the mRNA, but it is the aminoacyl-tRNA synthetase that performs the actual linking of the amino acid to the tRNA.
Different cells can have 40 to 60 types of tRNAs, each with a three-nucleotide anticodon that pairs with codons during protein synthesis. The specificity is largely due to the unique structure of both the aminoacyl-tRNA synthetase and the tRNA, which allows them to fit together like a key in a lock. Once together, the enzyme catalyzes the attachment of the amino acid to the tRNA, using ATP in the process.
Overall, the relationship between tRNAs, aminoacyl-tRNA synthetases, and amino acids plays a critical role in translating the genetic code into functional proteins, with the synthetases being the decisive factor in which amino acid is added to the polypeptide chain in the making.