What is keratin primarily made of?

Keratin is primarily made of a fiber protein, which is the correct answer. This structural protein is a key component of hair, skin, and nails, providing them with strength and resilience. Keratin's fibrous structure allows it to form protective layers in epithelial cells, which are crucial for maintaining the integrity of these tissues.

The composition of keratin consists of long chains of amino acids that fold into specific three-dimensional shapes, contributing to its mechanical properties and resilience. This characteristic makes keratin vital for protecting the body against external environmental factors such as injury, pathogens, and dehydration.

In contrast, carbohydrates, lipids, and nucleic acids serve different functions in biological systems. Carbohydrates are primarily involved in energy storage and structural components in cells, lipids serve as energy reserves and structural components of cell membranes, while nucleic acids are crucial for genetic information storage and transfer. Each of these macromolecules fulfills distinct roles in the body, differentiating them from keratin, which is specifically classified as a fiber protein.