Endoplasmic reticulum is a network of interconnecting membranous structures filled with fluid. Which of the following cells would most likely have high concentration of densely packed rough endoplasmic reticulum?

Options

A. A bioluminescent bacterial cell
B. A functional phloem at maturity
C. An amoeba engulfing small ciliates
D. A pancreatic cell engaged in the production of digestive enzymes

Explanation

To determine which type of cell would most likely have a high concentration of densely packed rough endoplasmic reticulum (RER), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure and Function of Endoplasmic Reticulum (ER)**:
- The endoplasmic reticulum is a network of interconnecting membranous structures filled with fluid.
- It has two types: Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER).
- RER is studded with ribosomes on its surface, which gives it a "rough" appearance.

2. **Identify the Function of Rough Endoplasmic Reticulum**:
- The primary function of RER is protein synthesis. The ribosomes attached to the RER are responsible for translating mRNA into proteins.

3. **Consider the Types of Cells**:
- Think about which cells are involved in high levels of protein synthesis. Cells that secrete proteins or enzymes will have a higher concentration of RER.
- Examples of such cells include pancreatic cells, which produce digestive enzymes.

4. **Evaluate the Options**:
- **Option 1: Bio-luminescent bacterial cell** - These cells do not primarily focus on protein synthesis related to digestive enzymes.
- **Option 2: Phloem cells** - These are plant cells involved in the transport of nutrients, not specifically involved in high protein synthesis.
- **Option 3: Amoeba engulfing small ciliates** - This process involves phagocytosis, not high protein synthesis.
- **Option 4: Pancreatic cells** - These cells are known for producing and secreting digestive enzymes, indicating a high need for protein synthesis.

5. **Conclusion**:
- Based on the functions and the types of cells, **pancreatic cells** would most likely have a high concentration of densely packed rough endoplasmic reticulum.

### Final Answer:
**Pancreatic cells** would most likely have a high concentration of densely packed rough endoplasmic reticulum.

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