A linear (simple line) polypeptide chain
Polypeptide chain shaped into coils (alpha helix) & pleats (beta sheet)
Many coils & sheats in 3D! (THREE --> TERTIARY --> 3D)
Many tertiary structures combined with non-proteins, forming a complex protein molecule.
TEACHING & MEMORIZING TIPS: Use country analogy to remember the structures' levels:
Primary: Taman Melawati
Secondary: Ulu Klang