week 3: 10.4 the contraction cycle and cross bridge formation

Question 1

1. contraction cycle begins

Answer 1

begins with the arrival of calcium ions within zone of overlap in sarcomere

Question 2

2. active sight exposure

Answer 2

calcium ions bind to troponin weakening the bond between actin and the troponin-tropomyosin complex
troponin then changes position rolling the tropomyosin molecule away from the active sites on actin and allowing interaction with energised myosin heads

Question 3

cross bridge formation

Answer 3

once active sights are exposed, energised myosin heads bind to them

Question 4

myosin heads pivoting

Answer 4

after cross-bridge formation, energy that was stored in resting state is released as the myosin head pivots towards the M line (power stroke)
when power stroke occurs, the bound ADP and phosphate group are released

Question 5

5. cross bridge detachment

Answer 5

when another ATP binds to the myosin head, the link between the myosin head and active site on the actin molecule is broken, active site is now exposed and able to form another cross-bridge

Question 6

6. myosin reactivation

Answer 6

free myosin head splits ATP into ADP and P
energy released used to recock the myosin head