What causes the myosin binding site of an actin molecule to be exposed? A. ATP attaching to the myosin cross-bridge B. a nerve impulse reaching the motor end plate of a motor nerve. C. calcium ions attaching to troponin D. acetylcholine crossing the neuromuscular junction
Option C: Calcium causes an alternate of form to the troponin molecule while they attach. This causes troponin to wrench tropomyosin farfar from its resting posi- tion masking the binding site.
