Question

Myosin filament has a fixed length of?

• A. 0.16 nm
• B. 1.6 micrometers
• C. 16 nm
• D. 1.6 mm

Hint:

Thick myosin filament is fixed at about 1.6 micrometers; thin actin about 1 micrometer.

Answer 1

The Correct Option is B

Step 1: In striated (skeletal) muscle, the thick filament is composed of myosin. Its length is uniform and fixed throughout the muscle.

Step 2: The total length of each myosin (thick) filament is almost exactly 1.6 micrometers. This contrasts with the thin (actin) filaments, which are about 1.0 micrometer long.

Step 3: Checking the units rules out the distractors: 0.16 nm and 16 nm are far too small (subatomic to molecular scale), and 1.6 mm is far too large for a single filament. Only 1.6 micrometers is the physiologically correct dimension.

Step 4: Therefore the fixed length of the myosin filament is 1.6 micrometers, option (b).