Which of the following criteria does not pertain to facilitated transport

Options

A. Transport saturation
B. Uphill transport
C. Requirement of special membrane proteins
D. High selectivity

Answer

To determine which of the following criteria does not pertain to facilitated transport, we need to analyze each option provided in the question. The options are:

1. Transport saturation
2. Uphill transport
3. Requirement of spatial membrane proteins
4. High selectivity

**Step-by-step Solution:**

1. **Understanding Facilitated Transport**: Facilitated transport, also known as facilitated diffusion, is a process that allows substances to cross membranes with the assistance of special proteins. It typically occurs down the concentration gradient, meaning from an area of higher concentration to an area of lower concentration.

2. **Evaluating Each Option**:
- **Transport Saturation**: This criterion pertains to facilitated transport. In facilitated diffusion, there are carrier proteins that can become saturated when all binding sites are occupied, limiting the rate of transport.
- **Uphill Transport**: This does not pertain to facilitated transport. Uphill transport refers to moving substances against their concentration gradient (from lower to higher concentration), which requires energy (active transport), not facilitated diffusion.
- **Requirement of Spatial Membrane Proteins**: This is a characteristic of facilitated transport. Specific proteins embedded in the membrane are essential for transporting substances across the membrane.
- **High Selectivity**: This criterion is also relevant to facilitated transport. The transport proteins are selective for specific molecules, allowing only certain substances to pass through.

3. **Conclusion**: Based on the analysis, the option that does not pertain to facilitated transport is **Uphill Transport**. This is because facilitated transport occurs down the concentration gradient, not against it.

**Final Answer**: Uphill transport does not pertain to facilitated transport.

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