Keratin is a strong fibrous protein that forms the main structural component of various hard and protective tissues in many animals, including humans.
What Structures Contain Keratin?
Numerous body parts and animal structures are made of keratin. These include:
- Human Structures: Hair, nails, and the outermost layer of skin are primarily composed of keratin. This protein provides strength, protection, and a waterproof barrier.
- Animal Structures: Keratin forms the structural foundation of animal horns (such as those found on sheep, goats, and cattle), hoofs, claws, wool, feathers, and the beaks of birds. Even the baleen plates in the mouths of baleen whales are keratin-based. Rhino horns are also made of keratin, contrary to popular belief that they're bone.
Keratin's Composition and Properties
It's crucial to understand that keratin is not a single substance. Rather, it's a family of proteins. The specific types and arrangements of these proteins result in the varying properties observed in different keratinous structures. For instance, the keratin in hair is different from the keratin in nails, giving each its unique characteristics. The differing keratin types contribute to the wide range of hardness and flexibility seen in structures composed of this protein.
Examples and Practical Insights
Let's highlight some specific examples:
- Hair: The strength and elasticity of hair are due to its keratin content.
- Nails: Keratin makes nails tough and resistant to damage, enabling them to protect the sensitive fingertips.
- Horns: The horns of various animals, like sheep and cattle, serve as protective structures and weapons, thanks to their strong keratin composition. Note that true horns are made of keratin, but other types of horns (like those of rhinos) are different.
- Feathers: The structure and stiffness of bird feathers are dependent upon their keratin content.
- Baleen: Whale baleen, used for filter feeding, is a remarkable example of a flexible yet strong keratin structure.
