Which one is required for muscle contraction and nerve impulse transmission ?

Options

A. `Ca^(2+)`
B. `Mg^(2+)`
C. `Fe^(2+)`
D. Both A and B.

Answer

To solve the question "Which one is required for muscle contraction and nerve impulse transmission?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Muscle Contraction**:
- Muscle contraction primarily involves the interaction of actin and myosin filaments within muscle fibers. Calcium ions (Ca²⁺) play a crucial role in this process.
- When a muscle is stimulated, calcium ions are released from the sarcoplasmic reticulum into the muscle cell, allowing the contraction process to begin.

2. **Understanding Nerve Impulse Transmission**:
- Nerve impulse transmission involves the movement of ions across the neuronal membrane.
- Calcium ions are essential for the release of neurotransmitters at the synaptic terminals, which is a critical step in transmitting nerve impulses.

3. **Identifying the Ions**:
- The question provides options: calcium ions, magnesium ions, iron ions, and both A and B.
- We know that calcium ions are required for both muscle contraction and nerve impulse transmission.

4. **Considering Other Options**:
- Magnesium ions are important in various biochemical reactions, including those involving ATP, but they are not directly required for muscle contraction or nerve impulse transmission.
- Iron ions are primarily involved in oxygen transport and are not directly related to muscle contraction or nerve impulse transmission.

5. **Conclusion**:
- Since calcium ions are required for both muscle contraction and nerve impulse transmission, the correct answer is "calcium ions".

### Final Answer:
- Calcium ions are required for muscle contraction and nerve impulse transmission.