Which of the following methods for transporting substances across a membrane does not involve a change in shape of transport protein

Options

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

Answer

To solve the question of which method for transporting substances across a membrane does not involve a change in the shape of transport proteins, we can analyze the options provided:

1. **Facilitated Diffusion**: This process involves transport proteins that help move substances across the membrane. When substances bind to these proteins, the proteins undergo a conformational change to transport the substance. Therefore, this method does involve a change in the shape of the transport protein.

2. **Simple Diffusion**: This is the process where substances move directly through the lipid bilayer of the membrane without the assistance of transport proteins. Since no transport proteins are involved in this process, there is no change in shape of any transport protein.

3. **Active Transport**: This method requires energy to move substances against their concentration gradient, typically involving transport proteins. These proteins change shape to transport the substance across the membrane, indicating that this method does involve a change in the shape of the transport protein.

4. **Sodium-Potassium Pump**: This is a specific example of active transport where sodium ions are pumped out of the cell and potassium ions are pumped in. This process also requires the transport protein to change shape to move the ions across the membrane, thus involving a change in the shape of the transport protein.

Based on this analysis, the method that does not involve a change in the shape of transport proteins is **Simple Diffusion**.

### Final Answer:
**Simple Diffusion** is the method for transporting substances across a membrane that does not involve a change in shape of transport proteins.