Outermost layer of cell wall is

Options

A. primary wall
B. Secondary wall
C. Tertiary wall
D. Middle lamella , if present

Answer

To answer the question "What is the outermost layer of the cell wall?", we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the Cell Wall Structure**:
- The cell wall is a protective layer surrounding the cell membrane in plant cells, fungi, and some prokaryotes. It is important to know that the cell wall is not a single layer but consists of multiple layers.

2. **Identifying the Layers of the Cell Wall**:
- The cell wall typically has three main layers:
- **Primary Cell Wall**: This is the outermost layer, which is thin and flexible.
- **Secondary Cell Wall**: This layer is located beneath the primary cell wall and is thicker and more rigid.
- **Middle Lamella**: This layer acts as a cementing substance between adjacent cells, often made of pectins.

3. **Determining the Outermost Layer**:
- Among the layers mentioned, the primary cell wall is the first layer that is encountered when looking from the outside of the cell. It is the outermost layer of the cell wall.

4. **Conclusion**:
- Therefore, the correct answer to the question is **A. Primary Wall**.

### Final Answer:
The outermost layer of the cell wall is **A. Primary Wall**.

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