Which structural organizations are always present in proteins? A - Primary and Secondary B - Secondary and Tertiary C - Tertiary and Quaternary D - Primary and Tertiary

A. Primary and Secondary

Explanation:

This is because these are the two most basic and lowest levels of structural organization in proteins and therefore shared amongst all proteins. Primary structure is simply a chain of amino acids, secondary structure is either an alpha-helix or a beta-pleated (accordion) sheat formed by hydrogen bonds between the backbones of the primary structure protein, tertiary is just a 3d shape formed by the interactions of R groups of the amino acids, and quarternary is still 3d but made up of 1 or more sub 3-d shapes.