[Campbell Biology P.1181] According to the passage, what molecule directly activates an enzym... | Practice Question

According to the passage, what molecule directly activates an enzyme that phosphorylates the myosin head, enabling smooth muscle contraction?

  • A: Troponin
  • B: Actin
  • C: Calmodulin
  • D: ATP

Explanation

The passage states: 'Calcium ions cause contraction by binding to the protein calmodulin, which activates an enzyme that phosphorylates the myosin head, enabling cross-bridge activity.' Therefore, calmodulin is the direct activator.