tRNA activating enzymes

each tRNA molecule is recognized by a tRNA-activating enzyme that attaches a specific amino acid to the tRNA, using ATP for energy
- activation involves attaching an amino acid to the 3' terminal to the tRNA
- there are 20 d/t tRNA-activating enzymes for each of the 20 amino acids
energy from ATP is needed for the attachment of amino acids
once the amino acid is attached, the amino acid is activated by the formation of a bond between the enzyme and adenosine monophosphate (AMP)
- the activated amino acid is then covalently attached to the tRNA
  - energy from this bond is later used to link the amino acid to the growing polypeptide chain during translation