Difficulty: Medium
Average Score: 71%
Entry Exam
Passage / Scenario
Which of the following ions binds to the troponin complex, initiating muscle contraction?
Correct answer
D
Rationale
The correct answer is calcium (D). Calcium ions bind to the troponin complex, initiating muscle contraction. When calcium binds to troponin, it causes a conformational change in the troponin-tropomyosin complex, exposing the binding sites on actin for myosin. This interaction allows muscle contraction by facilitating the sliding of actin and myosin filaments past each other, leading to muscle contraction.