system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Keratin is present in both skin and nail. However, skin is much more flexible than the nail. This is because keratin of skin has?
assistant
The correct answer is  Keratins are fibrous proteins present in hair, skin and nails, horn, hoof, etc. They mainly have the alpha helical structure. Each fibril has 3 polypeptide chains and each bundle has about 10-12 bundles. The matrix has cysteine-rich polypeptide chains which are held together by disulfide bonds. The more the number of disulfide bonds, the harder the keratin is. This is the reason behind skin is more flexible than nail. Ref: Essentials of Medical Biochemistry: With Clinical Cases By N. V. Bhagavan, Chung-Eun Ha, 2011, Page 33