Which of the following ions binds to the troponin complex, initiating contraction of a muscle?
A.
Potassium.
B.
Calcium.
C.
Phosphorus.
D.
Sodium
The ion that binds to the troponin complex, initiating muscle contraction, is:
B. Calcium
Explanation: In muscle contraction, calcium ions (Ca²⁺) bind to the troponin complex on the actin filaments. This binding causes a conformational change in the troponin-tropomyosin complex, which exposes the binding sites on actin for myosin, leading to muscle contraction.