Sarcoplasmic reticulum is

Options

A. E.R. of muscle cell
B. E.R. of nerve cell
C. Reticulum of hereditary material
D. none of these

Answer

**Step-by-Step Solution:**

1. **Understanding Sarcoplasmic Reticulum**: The sarcoplasmic reticulum (SR) is a specialized type of endoplasmic reticulum found in muscle cells. It plays a crucial role in muscle contraction.

2. **Identifying the Correct Option**:
- The first option states that the sarcoplasmic reticulum is the endoplasmic reticulum of muscle cells. This is correct because the SR is indeed a modified form of the endoplasmic reticulum that is specifically adapted for muscle function.
- The second option suggests that it is the endoplasmic reticulum of nerve cells. This is incorrect, as the sarcoplasmic reticulum is not found in nerve cells.
- The third option refers to it as the reticulum of hereditary material, which is also incorrect.
- The last option states "none of these," which is incorrect as well.

3. **Conclusion**: The correct answer is the first option: "ER of muscle cell." The sarcoplasmic reticulum is essential for storing and releasing calcium ions, which are vital for muscle contraction.

**Final Answer**: Sarcoplasmic reticulum is the endoplasmic reticulum of muscle cells.

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