Which statement about the primary structure is most accurate regarding enzyme function?

Which statement about the primary structure is most accurate regarding enzyme function?

• A. It is irrelevant to enzyme function
• B. It only forms secondary structure
• C. It is identical in all organisms
• D. It determines the three-dimensional structure including the active site

Answer: (D)

The first level of a protein’s structure is the sequence of amino acids linked in a chain. That linear order sets up how the chain will fold into its three-dimensional shape. The way it folds brings specific amino acids into close proximity to form the active site—the pocket where the substrate binds and the chemical reaction occurs. Because the active site’s shape and chemistry come directly from how the chain folds, the order of amino acids in the primary structure determines the enzyme’s function. If the sequence changes, the folding pattern can change too, altering or destroying the active site and thereby changing or eliminating catalytic activity. While secondary structures like helices and sheets appear because of the same sequence, they are parts of the bigger folding process that ultimately defines the active site. The primary structure is not identical in all organisms; sequences vary, though many enzymes are conserved, differences in sequence can lead to differences in folding and function.

The first level of a protein’s structure is the sequence of amino acids linked in a chain. That linear order sets up how the chain will fold into its three-dimensional shape. The way it folds brings specific amino acids into close proximity to form the active site—the pocket where the substrate binds and the chemical reaction occurs. Because the active site’s shape and chemistry come directly from how the chain folds, the order of amino acids in the primary structure determines the enzyme’s function.

If the sequence changes, the folding pattern can change too, altering or destroying the active site and thereby changing or eliminating catalytic activity. While secondary structures like helices and sheets appear because of the same sequence, they are parts of the bigger folding process that ultimately defines the active site. The primary structure is not identical in all organisms; sequences vary, though many enzymes are conserved, differences in sequence can lead to differences in folding and function.