Proteins

Step 1: Concept
Pepsin is a proteolytic enzyme found in the gastric juice of the stomach.
Step 2: Action
It acts on complex protein molecules to break them down into smaller units.
Step 3: Conclusion
The final product of protein digestion by pepsin is amino acids.
Final Answer: (A)

Step 1: Concept
Proteins are polymers of amino acids linked by polypeptide bonds.
Step 2: Analysis
Wool, hair, and nails are made of fibrous proteins (keratin).
Step 3: Analysis
DNA is a nucleic acid, which is a polymer of nucleotides and contains no polypeptide bonds.
Step 4: Conclusion
Therefore, DNA is not a protein.
Final Answer: (D)

Step 1: Understanding the Concept:
Myosin is a major component of muscle fibers and is a motor protein. Proteins are classified into fibrous and globular based on structure.

Step 2: Detailed Explanation:
Myosin is a fibrous protein. It has a long, rod-like tail (fibrous domain) and a globular head domain that binds to actin and hydrolyzes ATP. While it has a globular region, the overall protein is classified as fibrous due to its elongated shape and structural role in muscle contraction. It is not an enzyme in the typical sense, though the head domain has ATPase activity.

Step 3: Final Answer:
Myosin is a fibrous protein, which corresponds to option (A).