Question

question 33
when a muscle cell is relaxed:
a the cross bridges are bound to calcium
b the cross bridges are unable to bind to actin
c the cross bridges are attached to actin
d the cross bridges are bound to troponin

Explanation:

When a muscle cell is relaxed, troponin - tropomyosin complex covers the myosin - binding sites on actin. So, the cross bridges (myosin heads) are unable to bind to actin.

Answer:

B. the cross bridges are unable to bind to actin