Which type of proteins is most likely to be fibrous?

Fibrous proteins are characterized by their elongated, thread-like structures that provide support and strength to various biological tissues. Collagen and keratin are classic examples of fibrous proteins.

Collagen is the main structural protein found in connective tissues such as tendons, ligaments, and skin, contributing to their strength and resilience. Keratin is a key structural component in hair, nails, and the outer layer of skin, providing protective and structural functions.

In contrast, enzymes (which are typically globular proteins) are more about facilitating biochemical reactions rather than providing structural support. Receptors and membrane channels also fall into the category of globular proteins; they are primarily involved in signaling and transport across cell membranes, respectively, rather than providing the structural integrity associated with fibrous proteins.

This distinction clarifies why collagen and keratin are the most representative of fibrous proteins, making them the correct choice in this context.