The tertiary structure is the 3D shape of a single protein chain. After forming helices and sheets (secondary structure), the protein folds further to get a unique shape.

• This 3D shape is stabilized by hydrogen bonds, ionic interactions, disulfide bridges, and hydrophobic interactions.
• The shape is crucial for the protein’s function - enzymes, antibodies, or structural proteins rely on this specific folding.

If the tertiary structure is wrong, the protein cannot work properly, leading to diseases like sickle cell anemia or enzyme deficiencies.