A student simulates muscle contraction in a model using the following order of events:
1.Calcium pumps of the sarcoplasmic reticulum open.
2.Tropomyosin moves.
3.Calcium ions bind to troponin.
4.Myosin heads bend to attach to actin filaments.

Based on the order of steps in the student's model, will the muscle successfully contract?

Question

A student simulates muscle contraction in a model using the following order of events:
1.Calcium pumps of the sarcoplasmic reticulum open.
2.Tropomyosin moves.
3.Calcium ions bind to troponin.
4.Myosin heads bend to attach to actin filaments.


Based on the order of steps in the student's model, will the muscle successfully contract?

anonymous · Answer

@sleepyjess @KAKES1967 please helppppp.

anonymous · Answer

I think it's A

alphabeta · Answer

Without being completely sure, I would think that the correct order is to switch 2 and 3. Tropomyosin sits outside of the actin which blocks the binding sites (where the myosin head will bind), so the calcium ions need to bind to troponin (number 3), which will cause the tropomyosin to move (number 2).