Final answer:
Protein Structure Levels: primary, secondary, tertiary, quaternary. The primary structure is the sequence of amino acids in the polypeptide chain. It determines the higher levels of protein structure.
Step-by-step explanation:
Protein Structure Levels
Proteins have four levels of structure: primary, secondary, tertiary, and quaternary. The primary structure of a protein refers to the sequence of amino acids in its polypeptide chain. This sequence is encoded in genes and determines the higher levels of protein structure.
For example, the primary structure of insulin, a protein with 51 amino acids, is shown in Figure 18.6.1. The secondary structure consists of regular repeating local structures formed by hydrogen bonding, such as alpha-helices and beta-pleated sheets. The tertiary structure is the overall three-dimensional folding of a protein, and the quaternary structure refers to the arrangement of multiple polypeptide chains in a protein.