Final answer:
Adenine nucleotides are added by an enzyme complex containing various proteins, such as aminoacyl-tRNA synthetase and adenosine monophosphate (AMP).
Step-by-step explanation:
Adenine nucleotides, such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP), are added by an enzyme complex that contains several proteins. These proteins include aminoacyl-tRNA synthetase, which binds to a tRNA molecule and adds the correct amino acid to the tRNA, and adenosine monophosphate (AMP), which is an adenine molecule bonded to a ribose.