Design a protein with a specific function by describing its primary, secondary, tertiary, and quaternary structures.

A protein with a primary structure of random amino acids, secondary structure of beta sheets, tertiary structure forming a linear shape, and no quaternary structure.

A protein with a primary structure of hydrophilic amino acids only, secondary structure of alpha helices, tertiary structure forming a fibrous shape, and quaternary structure with three subunits.

A protein with a primary structure of identical amino acids, secondary structure of random coils, tertiary structure forming a flat shape, and quaternary structure with multiple identical subunits.

A protein with a primary structure of alternating hydrophobic and hydrophilic amino acids, secondary structure of alpha helices, tertiary structure forming a globular shape, and quaternary structure with two subunits for binding.