[Campbell Biology P.1187] During vertebrate skeletal muscle contraction, what is the primary ... | Practice Question

During vertebrate skeletal muscle contraction, what is the primary role of calcium ions?

  • A: To break cross-bridges as a cofactor in hydrolysis of ATP.
  • B: To bind to troponin, exposing myosin-binding sites.
  • C: To transmit action potentials to the muscle fiber.
  • D: To spread action potentials through the T tubules.

Explanation

During skeletal muscle contraction, calcium ions are released from the sarcoplasmic reticulum and bind to troponin, which then causes tropomyosin to move, exposing the myosin-binding sites on the actin filaments. This allows myosin heads to form cross-bridges and initiate contraction.