The structure of a fibrous protein comprises of polypeptide chains in the form of:

Explanation

Fibrous proteins are distinguished by their long, thread-like strands or fibrils. These proteins have a repeating pattern of secondary structures, such as alpha helices or beta sheets, aligning along the protein's length. This alignment imparts tensile strength and structural integrity, making fibrous proteins crucial for support and structure in various biological tissues and cells. In contrast, the other options-cluster, spherical or curled up ball, and flat uncoiled chains-do not describe the structural features of fibrous proteins, which are known for their extended, fibrous configuration.