In facilitated diffusion

Options

A. the hydrolysis of ATP is required to facilitate diffusion
B. specific substances are transported against their concentration gradient.
C. membrane phospholipids create a channel that permits diffusion of a specific substance
D. a membrane protein binds to specific solute and then undergoes a conformational change.

Answer

**Step-by-Step Solution:**

1. **Understanding Facilitated Diffusion:**
- Facilitated diffusion is a process that allows specific molecules to cross the plasma membrane with the help of membrane proteins. This process does not require energy (ATP) and occurs along the concentration gradient, meaning substances move from an area of higher concentration to an area of lower concentration.

2. **Analyzing the Options:**
- **Option A:** "The hydrolysis of ATP is required to facilitate diffusion."
- This statement is incorrect because facilitated diffusion does not require energy input; it relies on the concentration gradient.

- **Option B:** "Specific substances are transported against their concentration gradient."
- This statement is also incorrect. Facilitated diffusion only allows substances to move down their concentration gradient, not against it.

- **Option C:** "Membrane phospholipids create a channel that permits diffusion of a specific substance."
- This statement is misleading. While channels are involved, the transported molecules do not dissolve in the phospholipid bilayer; they pass through specific protein channels or carriers.

- **Option D:** "A membrane protein binds to a specific solute and then undergoes a conformational change."
- This statement is correct. In facilitated diffusion, membrane proteins (either channels or carriers) bind to specific solutes, undergo a conformational change, and allow the solute to pass through the membrane.

3. **Conclusion:**
- The correct answer is **Option D**. Facilitated diffusion involves membrane proteins that bind to specific solutes and change shape to transport them across the membrane.

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