Cross-Bridge cycle

Question 1

What immediately causes myosin to initiate the power stroke (pulling actin towards the M line)?

Answer 1

When ADP and inorganic phosphate are released from myosin

Question 2

What immediately causes myosin to detach from actin?

Answer 2

When ATP binds to myosin

Question 3

What are the steps of the Cross-bridge cycle?

Answer 3

1. Cross Bridge Formation
2. The power stroke
3. Cross Bridge detachment
4. Reactivation of myosin head

Question 4

What OCCURS during Cross Bridge Formation?

Answer 4

1. The activated myosin head binds to actin forming a cross bridge
2. inorganic phosphate is released and the bond between myosin + actin is stronger

Question 5

What OCCURS during the power stroke?

Answer 5

ADP is released and the activated myosin head pivots sliding the thin myofilament towards the center of the sarcomere

Question 6

What OCCURS during Cross Bridge Detachment?

Answer 6

when another ATP binds to the myosin head the link between the myosin head and actin weakens, and the myosin head detaches

Question 7

What OCCURS during the reactivation of myosin head?

Answer 7

1. ATP is hydrolyzed to ADP and inorganic phosphate
2. The energy released during hydrolysis reactivates the myosin head returning it to the cocked position