Most of the time, the parallel thick and thin filaments of the myofibrils are connected by ________ that span the space between myosin and actin molecules.
A) tropomyosin molecules
B) crossbridges
C) nebulin molecules
D) sarcomeres
E) calcium ions

Question

Quizplus · Accepted Answer

Crossbridges are the structures that span the space between myosin and actin molecules, connecting the parallel thick and thin filaments of the myofibrils. Crossbridges are formed by the myosin heads, which attach to actin during muscle contraction. Tropomyosin molecules and nebulin molecules serve other important roles in muscle function, but they do not directly connect the thick and thin filaments in this way. Sarcomeres are the repeating units of muscle fibers that contain thick and thin filaments, but they do not connect them. Calcium ions are involved in muscle contraction, but they do not physically connect the thick and thin filaments.

Most of the Time, the Parallel Thick and Thin Filaments