Respuesta :
Answer:
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.
Muscle Contraction occurs in both skeletal and smooth type of muscles. Although in smooth muscles, the contraction is slow as compared to skeletal muscles.
Contractions in skeletal and smooth muscles occurs: In skeletal muscle, calcium initiates contraction by binding to troponin, while in smooth muscle calcium initiates contraction by binding to calmodulin. (Option B)
Muscle contraction in both smooth and skeletal muscles is initiated and aided by the influx of calcium ions, the only difference is that in smooth muscle, the influx of calcium ion causes the ions to bind to intracellular calmodulin which causes the activation of an enzyme known as myosin kinase.
Although in skeletal muscles, the calcium ion binds to troponin changing the shape of tropomyosin exposing the myosin binding site
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