Final answer:
There are 20 different aminoacyl-tRNA synthetases in the cell, each corresponding to one of the 20 amino acids used in protein synthesis, making the statement true.
Step-by-step explanation:
The statement that there are 20 different aminoacyl-tRNA synthetases in the cell is indeed true. Each of the 20 amino acids that are incorporated into proteins has at least one corresponding aminoacyl-tRNA synthetase, which is responsible for charging the correct tRNA with its specific amino acid. The charging process consists of the amino acyl-tRNA synthetase first binding and hydrolyzing ATP to form a high-energy bond between an amino acid and adenosine monophosphate (AMP), then the activated amino acid is transferred to the correct tRNA, which subsequently participates in protein synthesis.