The cell organelle involved in the glycosylation of proteins is

Options

A. ribosome
B. peroxisome
C. mitochondrion
D. endoplasmic reticulum.

Explanation

**Step-by-Step Solution:**

1. **Understanding Glycosylation**: Glycosylation is a biochemical process where carbohydrate groups are attached to proteins. This modification is crucial for the proper functioning of proteins, influencing their stability, localization, and activity.

2. **Identifying the Organelle**: The organelle responsible for the glycosylation of proteins is the endoplasmic reticulum (ER). The ER exists in two forms: rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). The rough ER is particularly involved in the synthesis and modification of proteins.

3. **Role of the Rough Endoplasmic Reticulum**: The rough endoplasmic reticulum is studded with ribosomes on its cytoplasmic surface, which are the sites of protein synthesis. After proteins are synthesized, they enter the lumen of the RER, where glycosylation occurs. Various enzymes present in the RER facilitate the attachment of carbohydrate groups to the proteins.

4. **Conclusion**: Therefore, the cell organelle involved in the glycosylation of proteins is the endoplasmic reticulum, specifically the rough endoplasmic reticulum.

**Final Answer**: The cell organelle involved in the glycosylation of proteins is the **endoplasmic reticulum**.

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