This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
Keratin of skin is softer than keratin in nail because keratin in skin has 
Select and explain. 
A. Less number of disulphide bridges, B. Less number of salt bridges, C. High sodium content, D. Different affinity for water
A: Less number of disulphide bridges
Answer: A: Less number of disulphide bridges 
Explanation: Keratin in skin is softer than keratin in nail, horns because of lesser disulphide linkages between cysteine residues Ref: Biochemistry by U. Satyanarayana 3rd edition Pgno : 489