Question

When calcium ion binds to troponin,

tropomyosin moves into the groove between the helical actin strands.

troponin shifts to expose the active sites on actin.

myosin shortens.

muscle relaxation occurs.

active sites on the myosin are exposed.

Answer 1

Calcium ions binding to troponin initiate the muscle contraction process by displacing tropomyosin and exposing the myosin-binding sites on actin, enabling the contraction cycle as part of Excitation-Contraction Coupling.

Step-by-step explanation:

When calcium ions bind to troponin, a series of conformational changes occur within the muscle filament. This binding causes troponin to shift and move the tropomyosin away from the myosin-binding sites on the actin strands. As a result, the binding sites on actin are exposed, allowing myosin heads to attach, which is a crucial step in the muscle contraction cycle. Muscle contraction continues as long as ATP and calcium ions are available, allowing the myosin heads to pull the actin filaments and shorten the muscle. This is part of the process known as Excitation-Contraction Coupling, and it is essential for muscle contraction and relaxation.