Question

Which of the following is a globular protein?

• A. Collagen
• B. Myoglobin or Hemoglobin
• C. Myosin
• D. Fibroin

Hint:

Remember: Functional proteins (like enzymes, transporters) are usually globular; structural proteins (like collagen, keratin) are typically fibrous.

Answer 1

The Correct Option is B

Globular proteins are characterized by their compact, spherical shapes due to the folding of the polypeptide chains. They are typically soluble in water and perform a variety of functions, including those related to metabolism and immune response. Among the given options:

• Collagen: A fibrous protein providing structural support, not a globular protein.
• Myosin: Another fibrous protein primarily involved in muscle contraction.
• Fibroin: Known for its role in silk production, is a fibrous protein.
• Myoglobin or Hemoglobin: These are classic examples of globular proteins. Myoglobin stores oxygen in muscle cells, while hemoglobin carries oxygen in the blood.

Thus, Myoglobin or Hemoglobin is the correct choice as a globular protein.

Answer 2

Step 1: Understanding protein types
Proteins are broadly classified into two major types based on their shape and function:
Fibrous Proteins: Long, fiber-like, structural proteins that are generally insoluble in water.
Globular Proteins: Compact, spherical-shaped proteins that are mostly soluble in water and perform dynamic functions like transport, catalysis, etc. Step 2: Analyze each option
(A) Collagen: A fibrous protein found in connective tissues, cartilage, and bones. It provides tensile strength.
(B) Myoglobin or Hemoglobin: Both are globular proteins.
Myoglobin stores oxygen in muscles.
Hemoglobin transports oxygen in the blood. They are soluble in water and have a compact, globular structure.
(C) Myosin: A fibrous motor protein involved in muscle contraction. Though it has some globular heads, the overall structure is fibrous.
(D) Fibroin: A fibrous protein found in silk produced by silkworms. It forms beta-sheet structures. Step 3: Conclusion
Only option (B), "Myoglobin or Hemoglobin", fits the definition of a globular protein. Therefore, it is the correct answer.