The Living World 8th Edition by George Johnson

تمرين 15

Myofilaments can contract forcefully, pulling membranes attached to the two ends toward one another. Myofilaments cannot expand, however, pushing membranes attached to the two ends of a myofilament apart from one another. Why is it that myofilaments can pull but not push?
The role of calcium in the process of muscle contraction is to
A) gather ATP for the myosin to use.
B) cause the myosin head to shift position, contracting the myofibril.
C) cause the myosin head to detach from the actin, causing the muscle to relax.
D) expose myosin attachment sites on actin.