Final answer:
Keratin and collagen are both fibrous proteins that are insoluble in water: keratin is found in hair, nails, and skin, while collagen is in connective tissues. Fibrillin is involved in cell adhesion. The structure of these proteins is essential for their protective and structural functions in the body.
Step-by-step explanation:
In the context of protein structures, keratin, collagen, and fibrillin are proteins that have specific roles and structures. Keratin is classified as a fibrous protein and is a major component of hair, nails, and the outer layer of skin, meaning it is involved in protective functions. Collagen, another fibrous protein, is found in connective tissues throughout the body and serves a structural role, providing strength and support. On the other hand, fibrillin is essential for cell adhesion.
Both keratin and collagen are characterized by their fibrous and insoluble nature in water, reflecting their role in the body's structural integrity. These proteins differ from globular proteins, such as hemoglobin, which are more soluble and have a rounded shape. The fibrous nature of keratin and collagen means that their polypeptide chains are arranged parallel or nearly parallel to one another, forming tough materials crucial for the structural tissues such as tendons and bone, as well as skin and hair.