Final answer:
Protein structures consist of four levels: the primary structure is the sequence of amino acids, the secondary structure includes alpha-helix and beta-pleated sheet formations, the tertiary structure is the overall shape, and the quaternary structure involves multiple polypeptide chains. Protein function is determined by its structure. The correct option is A.
Step-by-step explanation:
The structure of a protein is crucial for its function and consists of four different levels: primary, secondary, tertiary, and quaternary.
Primary Structure of Protein
The primary structure refers to the sequence of amino acids in a protein. This sequence determines the protein's unique characteristics and the chemical properties of the polypeptide chain.
Secondary Structure of Protein
The secondary structure is the local folded structures stabilized by hydrogen bonds. The common types are the alpha-helix and beta-pleated sheet.
Tertiary Structure of Protein
The tertiary structure is the overall three-dimensional shape of a protein, resulting from interactions among the amino acids and the secondary structure.
Quaternary Structure of Protein
The quaternary structure is the arrangement of multiple polypeptide subunits into a single functional complex.
The function of the protein is intimately linked to its structure. Proteins can have structural roles, enzymatic roles, or be involved in signaling and transport.