So let's begin by focusing on fibrous protein. So what is a fibrous protein? Well, a fibrous protein or a structural protein basically consists of these long fibers that play a structural role in the cell and in our body. 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.