Which type of endoplasmic reticulum is more abundant (i) near the nucleus (ii) near the plasma membrane ?

Answer

To answer the question about which type of endoplasmic reticulum is more abundant near the nucleus and near the plasma membrane, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Types of Endoplasmic Reticulum**:
- There are two main types of endoplasmic reticulum (ER): Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER).
- RER is studded with ribosomes on its cytoplasmic surface, giving it a "rough" appearance, while SER lacks ribosomes and appears smooth.

2. **Function of Rough Endoplasmic Reticulum**:
- RER is primarily involved in the synthesis of proteins. The ribosomes on its surface are where protein synthesis occurs.
- Since the nucleus is the site where mRNA is produced and transported to ribosomes for translation, RER is typically found near the nucleus.

3. **Function of Smooth Endoplasmic Reticulum**:
- SER is involved in lipid synthesis, metabolism of carbohydrates, and detoxification of drugs and poisons.
- It is more abundant near the plasma membrane, where it plays a role in the synthesis of lipids that are incorporated into the cell membrane.

4. **Conclusion**:
- Therefore, the type of endoplasmic reticulum that is more abundant near the nucleus is **Rough Endoplasmic Reticulum (RER)**, while the type that is more abundant near the plasma membrane is **Smooth Endoplasmic Reticulum (SER)**.

### Final Answer:
- (i) Near the nucleus: Rough Endoplasmic Reticulum (RER)
- (ii) Near the plasma membrane: Smooth Endoplasmic Reticulum (SER)

---