Function of RER is

Options

A. Synthesis of proteins and their storage
B. Storage of proteins synthesized by cytoplasmic ribosomes
C. Storage of proteins and transportation in form of vesicle
D. Both (1) and (3)

Answer

### Step-by-Step Solution:

1. **Understanding RER**: The Rough Endoplasmic Reticulum (RER) is a type of endoplasmic reticulum that has ribosomes attached to its cytoplasmic surface, giving it a "rough" appearance.

2. **Function of RER**: The primary function of the RER is the synthesis of proteins. The ribosomes on the RER are the sites where amino acids are assembled into proteins based on the instructions encoded in mRNA.

3. **Analyzing Options**:
- **Option 1**: Synthesis of proteins - This is correct because the ribosomes on the RER are responsible for protein synthesis.
- **Option 2**: Storage of proteins synthesized by cytoplasmic ribosomes - This is incorrect. The RER does not store proteins made by cytoplasmic ribosomes; it primarily synthesizes its own proteins.
- **Option 3**: Storage of proteins and transportation in the form of vesicles - This is also incorrect. While the RER is involved in the synthesis of proteins, it does not store them; instead, proteins are transported to the Golgi apparatus for further processing and packaging.
- **Option 4**: Both 1st and 3rd - Since option 3 is incorrect, this option is also incorrect.

4. **Conclusion**: Based on the analysis of the options, the correct answer is **Option 1: Synthesis of proteins**.