Proteins are classified as fibrous or globular based on their structure and function. Fibrous proteins have elongated, thread-like structures, providing strength and support, while globular proteins are compact and often functional (e.g., enzymes).
Step 1: Define fibrous proteins
Fibrous proteins are insoluble in water, have repetitive amino acid sequences, and form structural components like hair, muscle fibers, or connective tissue.
Step 2: Analyze options
- (A) Keratin: A fibrous protein found in hair, nails, and skin, providing structural strength.
- (B) Insulin: A globular protein, a hormone regulating blood sugar, not fibrous.
- (C) Myosin: A fibrous protein in muscle fibers, responsible for muscle contraction.
- (D) Both (A) and (C): Since keratin and myosin are fibrous, this option is correct.
Step 3: Conclusion
Both keratin and myosin are fibrous proteins, matching option (D).