Endoplasmic reticulum is involved in all of the following except :

Options

A. production of ribosomes
B. synthesis of lipids
C. synthesis of proteins
D. transportation of molecules to the cell membrane for export

Explanation

**Step-by-Step Solution:**

1. **Understanding the Endoplasmic Reticulum (ER):**
- The endoplasmic reticulum is a vital cell organelle found in eukaryotic cells. It exists in two forms: rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).

2. **Functions of the Endoplasmic Reticulum:**
- The rough endoplasmic reticulum is primarily involved in the synthesis of proteins due to the presence of ribosomes on its surface.
- The smooth endoplasmic reticulum is involved in the synthesis of lipids and the metabolism of carbohydrates. It also plays a role in detoxification processes and the storage of calcium ions.

3. **Identifying the Exception:**
- The question asks for the function that the endoplasmic reticulum is NOT involved in.
- While the ER is involved in lipid synthesis, protein synthesis, and transportation of molecules, it does not play a role in the production of ribosomes.

4. **Conclusion:**
- Therefore, the correct answer to the question is that the endoplasmic reticulum is not involved in the production of ribosomes.

**Final Answer:**
- The endoplasmic reticulum is involved in all of the following except the production of ribosomes.

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