Final answer:
Proteins are classified as either fibrous or globular based on their shape and solubility. Fibrous proteins like keratin and collagen are insoluble and provide structural support in hair, skin, and connective tissues.
Step-by-step explanation:
Classification of Keratin, Collagen, and Fibroin
Proteins can be classified as either fibrous or globular, which describes the basic shape of the protein molecule. Fibrous proteins are typically insoluble in water and play key roles in structural, connective, and protective functions in the body. For instance, keratin is a fibrous protein that constitutes the hair, nails, and the outer layer of skin, providing strength and protection. Collagen, another fibrous protein, is essential for connective tissues and is known for its great tensile strength which provides resilience and strength to ligaments, tendons and also contributes to the structure of skin. Whereas fibroin, not explicitly mentioned in the descriptions provided, is known for its role in silk fibers, it similarly fits the fibrous proteins category, being an essential component of spider silk and silkworm silk.
Fibrous proteins such as keratin and collagen, form strong fibers and are involved in creating the structures that provide support and protection in various parts of the body. Keratin makes up the hair, nails, and the outer layer of the skin, serving as a protective barrier. Collagen fibers are secreted by fibroblasts and form long, straight fibers which resist stretching, contributing to the integrity of connective tissues.