The secondary structure folds up to form a 3-dimensional structure which looks like an inverted L.

One end of one L arm (the 3' end of the chain) is the acceptor stem. The other end of the L is the anti-codon loop that has to match the codon on the mRNA. The distance between the two ends of the L is ~ 7 nm. The corner of the L is used for correct positioning on the ribosome where the protein synthesis takes place.

In the tertiary (3-dimensional) structures of RNA, bases sometimes make hydrogen bonds with more than one partner, as illustrated in the picture above. These extra hydrogen bonds compensate for the distortion in the double-stranded helical regions when the RNA folds up and help stabilize the tertiary structure.

The covalent attachment between the tRNA and its corresponding amino-acid is achieved by yet another adaptor molecule (this time a protein molecule called aminoacyl-tRNA synthetase) of which there are at least 20 varieties, one for each kind of amino-acid. The synthetases recognize the detailed shape and properties of a specific amino-acid and the detailed shape of the acceptor stem in the folded tRNA molecule and catalyze the covalent attachment between the amino-acid and its corresponding tRNA.