Primary structure is defined as

Primary structure is defined as

• A. The amino acid sequence of the polypeptide, which denaturation does not change
• B. The three-dimensional folding of the chain
• C. The disulfide bond patterns
• D. The arrangement of multiple polypeptide chains

Answer: (A)

Primary structure is the linear order of amino acids in a polypeptide, held together by peptide bonds. Denaturation disrupts the folding patterns formed by noncovalent interactions, so it affects secondary, tertiary, and quaternary structure, but it does not break the peptide bonds that define the sequence. That’s why the amino acid sequence remains unchanged during denaturation, making it the definition of primary structure. The other ideas describe higher-level structures: three-dimensional folding corresponds to tertiary and possibly quaternary structure, disulfide bonds influence folding, and the arrangement of multiple polypeptide chains is quaternary structure.

Primary structure is the linear order of amino acids in a polypeptide, held together by peptide bonds. Denaturation disrupts the folding patterns formed by noncovalent interactions, so it affects secondary, tertiary, and quaternary structure, but it does not break the peptide bonds that define the sequence. That’s why the amino acid sequence remains unchanged during denaturation, making it the definition of primary structure. The other ideas describe higher-level structures: three-dimensional folding corresponds to tertiary and possibly quaternary structure, disulfide bonds influence folding, and the arrangement of multiple polypeptide chains is quaternary structure.