Tertiary Structure: the structure that a protein molecule forms when its atoms are arranged in space. Protein have multiple levels of structure. The most basic is its primary structure. A protein's primary structure is simply the order of its amino acids.

The tertiary structure of the protein Alcohol Dehydrogenase is shown above. Click on the image using your Right mouse button and change the Display of the molecule to Ribbons or Strands to see the winding and twisting typically found in a Protein's 3-D structure.