Question

question 5
polypeptides like membrane transport proteins have 3 - d structure. if we refer to hydrogen bonding between the amino and carboxyl groups of individual amino acids, then we are referring to
non - polar interactions in the primary structure.
covalent bonding in the primary structure.
polar interactions in the secondary structure.
polar interactions between r - groups.
polar interactions in the tertiary structure.

Explanation:

The primary structure of proteins is the linear sequence of amino - acids, held together by covalent peptide bonds. Secondary structure involves hydrogen - bonding patterns like alpha - helices and beta - sheets. Tertiary structure is the 3 - D folding of a single polypeptide chain, stabilized by various interactions including polar interactions between R - groups.

Answer:

polar interactions in the tertiary structure.