What is the primary structure of proteins?

The primary structure of proteins is defined as the specific sequence of amino acids that are linked together by peptide bonds to form a polypeptide chain. This sequence is crucial because it determines how the protein will fold into its higher-order structures—secondary, tertiary, and quaternary—ultimately influencing the protein's function. Each amino acid in the chain has a unique side chain that contributes to the properties of the protein, making the primary structure foundational to understanding protein chemistry.

Other choices, such as a chain of nucleotides, refer to nucleic acids like DNA and RNA, which are not proteins. A folded three-dimensional shape describes the tertiary and quaternary structures of proteins, where the primary sequence's information is utilized for folding. A complex of carbohydrates and lipids pertains to different biological molecules and interactions, not the structure of proteins. Thus, the primary structure's specificity as a sequence of amino acids is essential for protein function and stability.