Which of the following statements regarding contraction in skeletal and smooth muscle is TRUE?
A)In skeletal muscle,calcium initiates contraction by binding to troponin,while in smooth muscle calcium initiates contraction by binding directly to myosin.
B)In skeletal muscle,calcium ions bind to a regulatory protein on thin filaments;in smooth muscle,calcium ions bind to a regulatory protein on thick filaments.
C)In skeletal muscle,calcium initiates contraction by binding to myosin light-chain kinase,while in smooth muscle calcium initiates contraction by binding directly to tropomyosin.
D)In skeletal muscle,calcium initiates contraction by binding to troponin,while in smooth muscle calcium initiates contraction by binding to calmodulin.
E)All of the choices are true.

Question

Quizplus · Accepted Answer

In skeletal muscle, calcium initiates contraction by binding to troponin on the thin filaments, causing displacement of tropomyosin and exposure of myosin binding sites on actin. In smooth muscle, calcium initiates contraction by binding to calmodulin which activates myosin light-chain kinase, leading to phosphorylation of myosin and activation of contraction.

Which of the Following Statements Regarding Contraction in Skeletal and Smooth