Final answer:
The tertiary structure of proteins is formed by interactions between polypeptides, creating a three-dimensional shape.
Step-by-step explanation:
The correct answer is C) Tertiary, polypeptides, strands.
Proteins have four levels of organization: primary, secondary, tertiary, and quaternary structure.
The primary structure of a protein is its unique sequence of amino acids. The secondary structure refers to the local folding of the polypeptide chain into configurations such as alpha-helices and beta-pleated sheets.
The tertiary structure is the overall three-dimensional shape of the protein, which is determined by interactions between amino acid side chains that are far apart in the primary sequence. Quaternary structure refers to proteins made up of multiple polypeptide chains.