What is recognized by an aminoacyl trna synthetase?

The correct answer is: amino acid and tRNA(s) that correspond to that amino acid.

Aminoacyl-tRNA synthetase is an enzyme important for the process of translation (protein synthesis) because it attaches the amino acid onto its appropriate tRNA and forms aminoacyl-tRNA. There are 20 different aminoacyl-tRNA synthetases in humans, one for each amino acid of the genetic code and all of them use ATP as energy source for their function. After the aminoacyl-tRNA is formed, ribosome can transfer the amino acid from it onto a growing peptide (newly synthesized peptide, future protein).

cell/ tissue/ organ/ organ system/ body