Biology / Unit 13 Bio 3119 short lesson, about 20 seconds
Calcium, Troponin, and Tropomyosin
Captions available
The idea
At rest, tropomyosin blocks actin's myosin-binding sites; released calcium binds troponin, shifting tropomyosin aside and exposing those sites so the sliding cycle, per Bio 3115, can begin.
In practice
Calcium removal from the cytoplasm lets tropomyosin snap back over actin's sites, ending contraction.
Where people slip
Calcium enables contraction by exposing binding sites — it does not itself generate the pulling force.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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