Put the following events of the contraction cycle in the order in which they occur.
1) Cross-bridge detachment
2) Cross-bridge formation
3) Active site exposure
4) Myosin reactivation
5) Calcium ions bind troponin
6) Myosin head pivoting
A) 5,3,6,2,1,4
B) 5,3,2,6,4,1
C) 5,3,2,6,1,4
D) 5,3,6,2,4,1
E) 3,5,2,6,1,4

Question

Quizplus · Accepted Answer

The order of events in the contraction cycle is as follows:
1) Calcium ions bind troponin, causing a conformational change in tropomyosin, which exposes the active sites on actin.
2) Myosin heads bind to the exposed active sites on actin, forming cross-bridges.
3) The energy released from ATP hydrolysis causes the myosin head to pivot, moving the actin filament toward the center of the sarcomere.
4) Cross-bridge detachment occurs when a new ATP molecule binds to the myosin head, causing it to release from actin.
5) Myosin reactivation occurs when the energy from ATP hydrolysis is used to reposition the myosin head back into its high-energy state.
Therefore, the correct order of events is 5,3,2,6,1,4, and the best choice is C.

Put the Following Events of the Contraction Cycle in the Order