Question

approximately 80% of a muscle fibers volume are the myofibrils. this characteristic reflects muscles ability to _________.
a) produce relatively high amounts of atp
b) produce movement through contractile force
c) generate and propagate action potential
d) store oxygen molecules that can be used in aerobic respiration

Explanation:

Myofibrils are composed of contractile proteins (actin and myosin). Their large proportion (80% of muscle fiber volume) indicates their importance in muscle function. Muscle contraction, which is the basis for producing movement through contractile force, relies on the interaction of these proteins within myofibrils.

• Option A (producing ATP) is mainly related to mitochondria (the powerhouses of the cell for ATP production), not the high - volume presence of myofibrils.
• Option C (generating and propagating action potentials) is more about the muscle cell membrane (sarcolemma) and its ion channels, not the myofibrils' volume proportion.
• Option D (storing oxygen for aerobic respiration) is associated with myoglobin (an oxygen - storing protein in muscle cells), not myofibrils.

Answer:

B. produce movement through contractile force