Alpha-keratin is a protein present in

Alpha-keratin is a fibrous structural protein that forms the bulk of hair and wool; it is identified as the primary component of wool, hairs, hooves and nails [1]. Alpha-keratin is dominated by an alpha‑helical (coiled‑coil) structure and is especially prevalent in wool fibers, giving them strength and elasticity [2]. Therefore, among the given options, wool is the correct choice. Skin contains different epithelial (cyto-) keratins with distinct roles, and blood and eggs are not composed of filamentous alpha‑keratin structural fibers. The mechanical properties of alpha‑keratin in hair/wool arise from intermediate filament formation and disulfide cross‑links in cysteine‑rich keratin molecules.

Sources

1. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC7171262/
2. [2] https://www.researchgate.net/figure/Schematic-representation-of-keratin-based-materials-for-biomedical-applications_fig5_359516718