Proteins are essential to living organisms and contribute to structure.

• A. They are not involved in structure
• B. They contribute to structure and are essential
• C. They store genetic information
• D. They conduct electricity in water

Answer: (B)

Proteins play important structural roles in cells and tissues, and they are essential for life because of their diverse functions. Structural proteins like collagen and keratin provide strength and shape to tissues, while cytoskeletal proteins such as actin and tubulin organize the cell’s architecture and enable movement. At the same time, many proteins perform crucial jobs beyond structure—enzymes speed up chemical reactions, transport proteins move molecules across membranes, antibodies defend against pathogens, and receptors and signaling molecules coordinate communication inside the organism. Because proteins contribute to both the building blocks of tissues and the myriad processes that keep organisms alive, the statement that they contribute to structure and are essential best captures their broad and fundamental roles.

Storing genetic information is the job of nucleic acids (DNA and RNA), not proteins, so that option isn’t correct. The notion that proteins conduct electricity in water isn’t a defining feature of proteins; while some proteins participate in redox reactions, conductivity in water is generally about ions and electrochemical properties, not a general characteristic of proteins.