Which one is highly selective?

Options

A. Simple diffusion and Active transport
B. Active transport and facilitated diffusion
C. Simple diffusion and facilitated diffusion
D. Active transport and passive transport

Answer

To answer the question "Which one is highly selective?" in the context of transport in plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Selectivity in Transport**:
- In biological systems, selectivity refers to the ability of a transport mechanism to allow certain molecules to pass while excluding others.

2. **Role of Intrinsic Proteins**:
- Intrinsic proteins (also known as integral membrane proteins) play a crucial role in the selective transport of substances across cell membranes. They are embedded in the membrane and can facilitate the movement of specific molecules.

3. **Types of Transport Mechanisms**:
- There are several transport mechanisms in plants, including:
- **Simple Diffusion**: Movement of molecules from an area of higher concentration to an area of lower concentration without the need for proteins.
- **Facilitated Diffusion**: Movement of molecules across a membrane via intrinsic proteins, which is selective for specific molecules.
- **Active Transport**: Movement of molecules against their concentration gradient, requiring energy and specific intrinsic proteins.

4. **Identifying Highly Selective Mechanisms**:
- Among the transport mechanisms:
- **Simple Diffusion** is not selective as it allows any small molecules to pass through freely.
- **Facilitated Diffusion** and **Active Transport** are both highly selective because they involve specific intrinsic proteins that only allow certain molecules to pass through.

5. **Conclusion**:
- Therefore, the highly selective transport mechanisms in plants are **Facilitated Diffusion** and **Active Transport** due to the involvement of specific intrinsic proteins.

### Final Answer:
The highly selective transport mechanisms are **Facilitated Diffusion** and **Active Transport**.

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