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Muscle Physiology: Contraction Mechanisms · Zoology

In the cross-bridge cycle, what must happen before the myosin head can return to its 'high-energy' (cocked) position?

  1. Calcium must bind to the myosin tail region first
  2. ATP must be hydrolyzed into ADP and Pi
  3. The actin filament must rotate around its axis
  4. The Z-discs must approximate toward the M-line
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Correct answer: ATP must be hydrolyzed into ADP and Pi

Hydrolysis of ATP by the myosin head provides the energy necessary to 'cock' the head into its high-energy state. This energy is later used to drive the power stroke when the head binds to actin.

Difficulty: Medium Question 12 of 20

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