Which method of transport in plasma membrane does not require carrier molecule ?

Options

A. Active transport
B. Facilitated diffusion
C. Simple diffusion
D. `Na^(+)-K^(+)` pump

Answer

To answer the question, "Which method of transport in plasma membrane does not require a carrier molecule?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand Carrier Molecules**:
- Carrier molecules are proteins found in the plasma membrane that assist in the transport of substances across the membrane. They are essential for certain types of transport mechanisms.

2. **Identify Types of Transport**:
- There are various methods of transport across the plasma membrane, including active transport, facilitated diffusion, and simple diffusion.

3. **Active Transport**:
- Active transport requires energy (ATP) to move substances against their concentration gradient. This process involves carrier proteins, making it dependent on them.

4. **Facilitated Diffusion**:
- Facilitated diffusion is a type of passive transport that also requires carrier proteins to help move substances across the membrane, typically ions or larger molecules.

5. **Simple Diffusion**:
- Simple diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration without the need for energy or carrier molecules. This process occurs directly through the lipid bilayer of the membrane.

6. **Conclusion**:
- The method of transport that does not require a carrier molecule is **simple diffusion**. It allows substances to pass through the plasma membrane freely, relying solely on concentration gradients.

### Final Answer:
**Simple diffusion** is the method of transport in the plasma membrane that does not require a carrier molecule.