Question

question 47
2 points
___ is released from the sarcoplasmic reticulum and binds to ___ during the sequence of a
muscle contraction.
a calcium, tropomyosin
b sodium, troponin
c calcium, troponin
d sodium, tropomyosin

Explanation:

During muscle contraction, calcium ions ($Ca^{2+}$) are released from the sarcoplasmic reticulum. These calcium ions then bind to troponin. When calcium binds to troponin, it causes a conformational change that moves tropomyosin away from the myosin - binding sites on actin, allowing muscle contraction to occur. Sodium is mainly involved in processes like the action potential in neurons and muscle cells but not in the specific binding described here.

Answer:

C. calcium, troponin