Membrane system considered to be extension of infolded plasma membrane is

Options

A. Golgi complex
B. plastids
C. mitochondria
D. ER

Answer

To solve the question "Membrane system considered to be extension of infolded plasma membrane is," we will analyze each option provided and determine which one fits the description.

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for a membrane system that is an extension of the infolded plasma membrane. This means we are looking for a structure that is directly related to the plasma membrane and has a specific function in the cell.

2. **Analyze the Options**:
- **Option A: Golgi Complex**: The Golgi complex is involved in processing and packaging proteins but is not an extension of the plasma membrane. It is more of a separate organelle that modifies proteins received from the endoplasmic reticulum.

- **Option B: Plastid**: Plastids are double membrane-bound organelles found in plant cells, responsible for photosynthesis and storage of food. They do not originate from the infolded plasma membrane.

- **Option C: Mitochondria**: Mitochondria are also double membrane-bound organelles known as the powerhouse of the cell. They produce ATP but are not extensions of the plasma membrane.

- **Option D: Endoplasmic Reticulum (ER)**: The endoplasmic reticulum is a network of flattened, membrane-bound sacs that are continuous with the nuclear membrane. It is indeed considered an extension of the infolded plasma membrane and plays a crucial role in protein and lipid synthesis.

3. **Conclusion**: After analyzing all options, the endoplasmic reticulum (Option D) is the only structure that fits the description of being an extension of the infolded plasma membrane.

### Final Answer:
The correct answer is **Endoplasmic Reticulum** (Option D).

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