Question

multiple choice question

which protein links actin fibers to the inner face of the sarcolemma?

tropomyosin
titin
dystrophin
troponin

Explanation:

Identify the target protein function

The question asks for the specific protein that links actin thin filaments to the inner face of the sarcolemma (the muscle cell membrane).

Evaluate the role of Tropomyosin

Tropomyosin Regulation is a regulatory protein that wraps around actin filaments to block myosin-binding sites in a relaxed muscle. It does not link actin to the sarcolemma.

Evaluate the role of Titin

Titin Protein is a giant elastic protein that anchors thick myosin filaments to the Z discs, helping stabilize their alignment and providing elastic recoil.

Evaluate the role of Troponin

Troponin Function is a three-polypeptide complex bound to tropomyosin that binds calcium ions to initiate contraction. It does not anchor actin to the cell membrane.

Evaluate the role of Dystrophin

Dystrophin is a vital structural protein located just beneath the sarcolemma. It binds to actin filaments of the cytoskeleton on one end and to a complex of transmembrane proteins (dystrophin-glycoprotein complex) on the other, linking the internal contractile machinery to the extracellular matrix.

Answer:

• Tropomyosin
• Titin
• Dystrophin (Correct answer)
• Troponin