Chemical ions responsible for muscle contraction are

Options

A. (a) `Ca^(+ +)` and `K^(+)`
B. (b) `Na^(+)` and `K^(+)`
C. (c) `Na^(+)` and `Ca^(+)`
D. (d) `Ca^(+ +)` and `Mg ^( + +)` ions.

Answer

**Step-by-Step Solution:**

1. **Understanding Muscle Contraction:**
- Muscle contraction is a complex process that involves the interaction of various proteins and ions. The primary proteins involved are actin and myosin.

2. **Identifying Key Ions:**
- Among the various ions present in the body, calcium ions (Ca²⁺) play a crucial role in muscle contraction. They are essential for the activation of myosin and actin.

3. **Role of Calcium Ions:**
- Calcium ions bind to specific proteins (troponin and tropomyosin) on the actin filaments. This binding causes a conformational change that allows myosin heads to attach to actin, forming cross-bridges necessary for contraction.

4. **Involvement of Magnesium Ions:**
- Magnesium ions (Mg²⁺) also play a significant role in muscle contraction. They are important for ATPase activity, which is crucial for the energy supply required for muscle contraction.

5. **Eliminating Other Options:**
- Sodium (Na⁺) and potassium (K⁺) ions are primarily involved in generating action potentials in nerve cells and are not directly responsible for muscle contraction. Therefore, options involving sodium and potassium can be eliminated.

6. **Conclusion:**
- The correct pair of ions responsible for muscle contraction is calcium and magnesium ions. Thus, the correct answer is option D: calcium and magnesium ions.

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