<prompt> Alpha helix and Beta pleated sheet are examples ofPrimary structureSecondary structureTeiary structureQuaternary structure  <response>: 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: Harpers Illustrated Biochemistry, 30E 2015 pg no 38. 