Ribophorin-I and II occur on the surface of

Options

A. Rough E.R.
B. Smooth E.R.
C. Golgi body
D. None

Answer

To answer the question "Ribophorin-I and II occur on the surface of," we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Ribophorin**: Ribophorin-I and II are specific proteins that serve as receptors for the signal recognition particle (SRP) on the ribosomes. They play a crucial role in the process of protein synthesis and translocation.

2. **Identifying the Organelles**: The question provides four options:
- Rough Endoplasmic Reticulum (RER)
- Smooth Endoplasmic Reticulum (SER)
- Golgi Body
- None

3. **Function of Endoplasmic Reticulum**:
- The **Rough Endoplasmic Reticulum (RER)** is characterized by the presence of ribosomes on its cytoplasmic surface, which gives it a "rough" appearance. It is primarily involved in the synthesis of proteins that are either secreted from the cell or incorporated into the cell membrane.
- The **Smooth Endoplasmic Reticulum (SER)** lacks ribosomes and is involved in lipid synthesis and detoxification processes.
- The **Golgi Body** is involved in the modification, sorting, and packaging of proteins and lipids for secretion or delivery to other organelles.

4. **Locating Ribophorin**: Since ribophorin is associated with ribosomes, it is specifically found on the surface of the Rough Endoplasmic Reticulum (RER). The ribosomes attached to the RER are where protein synthesis occurs, and ribophorin serves as a receptor for the SRP during this process.

5. **Conclusion**: Based on the information gathered, the correct answer to the question is that Ribophorin-I and II occur on the surface of the Rough Endoplasmic Reticulum.

### Final Answer:
Ribophorin-I and II occur on the surface of the Rough Endoplasmic Reticulum (RER).

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