In cells actively participating in protein synthesis and secretion, which of the following organelles is frequently found ?

Options

A. Golgi complex
B. Smooth endoplasmic reticulum
C. Rough endoplasmic reticulum
D. Mitochondria

Answer

To solve the question regarding which organelle is frequently found in cells actively participating in protein synthesis and secretion, we can analyze each option provided:

1. **Golgi Complex**:
- The Golgi complex is known as the "post office" of the cell. It is primarily involved in modifying, sorting, and packaging proteins for secretion or delivery to other organelles. However, it does not directly participate in the synthesis of proteins; instead, it functions after proteins have been synthesized.

2. **Smooth Endoplasmic Reticulum (SER)**:
- The smooth endoplasmic reticulum is involved in lipid synthesis and detoxification processes. It does not have ribosomes on its surface and is not directly involved in protein synthesis.

3. **Rough Endoplasmic Reticulum (RER)**:
- The rough endoplasmic reticulum is characterized by the presence of ribosomes on its surface, which are the sites of protein synthesis. It plays a crucial role in the synthesis of proteins that are either secreted from the cell or sent to lysosomes and the plasma membrane.

4. **Mitochondria**:
- Mitochondria are known as the powerhouse of the cell, primarily involved in cellular respiration and energy production. They do not play a direct role in protein synthesis.

**Conclusion**:
Based on the analysis, the organelle that is frequently found in cells actively participating in protein synthesis and secretion is the **Rough Endoplasmic Reticulum (RER)**.

### Step-by-Step Solution:
1. **Identify the function of each organelle**:
- Golgi Complex: Modifies and packages proteins.
- Smooth Endoplasmic Reticulum: Synthesizes lipids; no ribosomes.
- Rough Endoplasmic Reticulum: Synthesizes proteins; has ribosomes.
- Mitochondria: Produces energy; involved in respiration.

2. **Determine which organelle is involved in protein synthesis**:
- The Rough Endoplasmic Reticulum has ribosomes, which are essential for protein synthesis.

3. **Eliminate the other options**:
- Golgi Complex and Smooth Endoplasmic Reticulum do not synthesize proteins.
- Mitochondria are not involved in protein synthesis.

4. **Select the correct answer**:
- The Rough Endoplasmic Reticulum is the organelle frequently found in cells that are actively participating in protein synthesis and secretion.