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 is a 
Select and explain. 
A. Globular protein, B. Cylindrical protein, C. Fibrous protein, D. None of the above
C: Fibrous protein
Answer: C: Fibrous protein 
Explanation: Fibrous proteins: When the axial ratio of length: width of a protein molecule is more than 10, it is called a fibrous protein. Examples: a-keratin from hair, collagen.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 83