Final answer:
The correct answer is B: keratins are composed of 50% type I and 50% type II keratin proteins. They are a significant component of intermediate filaments, which help maintain cell structure, resist tension, and anchor cells at adherens junctions.
Step-by-step explanation:
Keratins are intermediate filaments that are not localized inside the nucleus, but they do play important roles in maintaining cell structure and resistance to tension. They anchor the intermediate filament network at the adherens junctions, and they are indeed composed of type I and type II keratin proteins. Intermediate filaments are crucial for maintaining cell shape and structure, providing tensile strength to tissues. Keratin strengthens structures such as hair, nails, and the epidermis of the skin. Importantly, intermediate filaments are also essential for anchoring organelles within cells and forming cell-to-cell junctions.
The correct answer to the question is B: are composed of 50% type I and 50% type II keratin proteins. This statement accurately represents the composition of keratins found in intermediate filaments. They are indeed made up of these two types of keratin proteins that contribute to the strength and integrity of cells, particularly in epithelial tissue. Intermediate filaments are also fundamental in anchoring cells together and resisting forces that might cause cellular damage or deformation.