Which of the following is NOT an example of a structural protein?

• A. Keratin
• B. Elastin
• C. Collagen
• D. Hemoglobin

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the concept of structural proteins. Structural proteins are responsible for providing support, strength, and shape to cells and tissues. Examples include keratin, elastin, and collagen, which are integral to the structure of skin, hair, connective tissues, and more.
2. Step 2: Review the function of each protein listed in the question. Keratin is a structural protein found in hair, nails, and skin. Elastin provides elasticity to tissues like skin and blood vessels. Collagen is a major structural protein in connective tissues, bones, and skin.
3. Step 3: Examine the function of hemoglobin. Hemoglobin is a globular protein found in red blood cells, primarily responsible for transporting oxygen throughout the body. It is not involved in providing structural support to tissues.
4. Step 4: Compare hemoglobin to the other proteins listed. Unlike keratin, elastin, and collagen, hemoglobin does not contribute to the physical structure or support of tissues. Its role is functional rather than structural.
5. Step 5: Conclude that hemoglobin is NOT a structural protein, as its primary role is oxygen transport rather than providing support or shape to tissues.