Question

Calcium ions bind to troponin.
Tropomyosin moves.
Calcium pumps of the sarcoplasmic reticulum open.
Myosin heads bend to attach to actin filaments.
What would be the correct order of the steps above?

Answer 1

1, 4, 3, 2
1, 2, 3, 4
3, 1, 2, 4
3, 2, 1, 4

Answer 2

Tropomyosin is the long, filamentous protein that blocks the myosin head binding sites on actin, meaning cross-bridges can't form and the muscle can't contract. Troposmyosin can be moved out of the way by troponin, but only if calcium binds to it first. The calcium is released from the sarcoplasmic reticulum in response to membrane depolarization of the the muscle cell.

Soooo...based on this what do you think the order is?

Answer 3

so it can't be a or b correct?

Answer 4

@matt101

Answer 5

Right. It's either C or D

Answer 6

C?

Answer 7

pumps open, calcium binds, tropomyosin moves, heads attach... correct?

Answer 8

That's right!

Answer 9

thank you! are you able to help me with a few more questions? @matt101

Answer 10

Sure! Just tag me in any other posts you need a hand with