[A] : Keratin is one of a group of fibrous in- soluble proteins (scelero proteins) found in ectodermal cells of animals, as in hair, horns and nails. Leather is almost pure keratin.
[R]: Cornification is a process occurring in vertebrate epidermis and epidermal struc- tures in which keratin replaces the cytoplasm of a cell.

Proteins can also be classified based on their shapes and solubility in water. (i) Fibrous proteins are long and stringy, and are in soluble in water. Their primary role in structural materials of animal tissues. Eg : Collagens, Elastins, Keratins, and Fibrins. (ii) Globular proteins are compact and spherical and are soluble in water example enzymes, hormones, antibodies, transport proteins respiratory proteins. Which of the following belongs to collagen