Question

Which among the following is a myofibrillar protein ? A. Elastin B. Glycolytic enzymes C. Connectins D. Desmin E. Actin

• A. A, B, C Only
• B. A and E Only
• C. C, D, E Only
• D. A, D, E Only

Hint:

Remember that myofibrillar proteins are specifically involved in the structure and function of muscle contraction.

Answer 1

The Correct Option is D

Step 1: Concept
Myofibrils are the contractile units within muscle cells (myocytes). They contain proteins that play crucial roles in muscle contraction. These proteins include structural components and regulatory elements.

Step 2: Meaning
Elastin is a protein found in connective tissues, providing elasticity to structures like blood vessels and skin. Glycolytic enzymes are involved in the metabolic pathway of glucose breakdown for energy production but are not specific to myofibrils. Connectins are gap junction proteins that facilitate communication between cells, not part of the myofibrillar structure. Desmin is a intermediate filament protein found within myofibrils and helps maintain their structural integrity during contraction. Actin is a thin filament protein essential for muscle contraction.

Step 3: Analysis
- Elastin (A) is incorrect as it is not a myofibrillar protein. - Glycolytic enzymes (B) are metabolic proteins, not part of the myofibrillar structure. - Connectins (C) are intercellular communication proteins and do not belong to myofibrils. - Desmin (D) is correct as it is an intermediate filament found within myofibrils. - Actin (E) is also correct as it is a thin filament protein essential for muscle contraction.

Step 4: Conclusion
Desmin and Actin are both myofibrillar proteins, while Elastin, Glycolytic enzymes, and Connectins are not. Final Answer: (D)