Alpha helix and Beta pleated sheet are examples of
Regions of ordered secondary structure arise when a series of aminoacyl residues adopt similar phi and psi angles. Extended segments of polypeptide (example, loops) can possess a variety of such angles. The angles that define the two most common types of secondary structure, the ` helix and the a sheet, fall within the lower and upper left-hand quadrants of a Ramachandran plot, respectively. Ref: Harper's Illustrated Biochemistry, 30E (2015) pg no 38.
Primary structure
Secondary structure
Teiary structure
Quaternary structure
Structure and function of protein