Study the following and identify the mismatch

Options

A. Simple diffusion — Transport saturates
B. Facilitated transport — Down hill transport
C. Active transport — Transport saturates
D. Both simple diffusion and facilitated transport — Metabolic energy is not required

Answer

To solve the question of identifying the mismatch among the options provided, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concepts**:
- **Simple Diffusion**: This is a passive transport process where molecules move from an area of higher concentration to an area of lower concentration without the need for energy (ATP).
- **Facilitated Diffusion**: This is also a passive process but involves transport proteins to help move molecules across the membrane. It also does not require energy.
- **Active Transport**: This process requires energy (ATP) to move substances against their concentration gradient, and it can reach a saturation point when all transport proteins are occupied.

2. **Analyze the Options**:
- The first option mentions "simple diffusion and transport saturates". This is incorrect because simple diffusion does not saturate; it continues as long as there is a concentration gradient.
- The second option refers to facilitated transport as "downhill transport", which is correct because it moves substances down their concentration gradient.
- The third option states that "active transport is a transport saturation", which is also correct as active transport can reach a saturation point when all transport proteins are utilized.
- The fourth option indicates that both simple diffusion and facilitated diffusion do not require metabolic energy, which is accurate.

3. **Identify the Mismatch**:
- The mismatch is in the first option: "simple diffusion and transport saturates". Simple diffusion does not exhibit saturation because it does not involve transport proteins.

4. **Conclusion**:
- The correct answer to the question of identifying the mismatch is the first option: "simple diffusion and transport saturates".