So some examples are intermediate filaments found in our cytoskeleton. We have collagen found in our connective tissue such as bone and we have carotene found in the hair and in our nails as well as in the wool of animals in the horns and in the claws of different kinds of animals. So in this lecture we're briefly going to focus on a specific type of keratin known as alpha carotene. So alpha carotene is the type of fibrous protein that is found in our hair and in our nails. Now, alpha carotene consists of these two individual and long fibers. These polypeptide chains as shown in the following diagram.