Place the following events in an order that could explain the origin of an earthquake. Label the first even "Step 1" and then the remaining events in order.

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Explanation:

B. In skeletal muscle, calcium initiates contraction by binding to troponin, while in smooth muscle calcium initiates contraction by binding to calmodulin.

Explanation:

The Calcium ions (Ca2 +) have a key role in skeletal muscle contraction. Moreover, the Troponins are regulatory proteins that also play roles in skeletal contraction. In this muscle, troponin is attached to tropomyosin, when Ca2 + binds to troponin it induces a conformational change, thereby exposing this protein to its binding to myosin filaments on the actin filaments, which initiates muscle contraction.  

On the other hand, calmodulin (calcium-modulated protein) is a protein which mediates the contractile state of the smooth muscle by binding Ca2+ ions. The function of this protein is to stimulate the development of force (contraction) in response to Ca2+ ions by activating the phosphorylation of myosin.