The carrier - mediated cotransport in which a solute is actively transported across a membrane against the gradient of electrochemical potential by coupling the uphill transport of one solute to the downhill transport of another in an example of

Options

A. Symport transport
B. Primary active transport
C. Facilitated diffusion
D. Antiport transport

Answer

To solve the question regarding carrier-mediated cotransport, we need to analyze the options provided and understand the definitions and mechanisms of each type of transport mentioned.

### Step-by-Step Solution:

1. **Understanding Cotransport**:
- Cotransport involves the simultaneous transport of two different solutes across a membrane. This can occur in two ways: symport (same direction) and antiport (opposite direction).

2. **Analyzing the Options**:
- **Option A: Symport Transport**:
- Symporters transport two different molecules in the same direction across the membrane. This does not fit the description of transporting one solute against its gradient while the other is transported downhill.
- **Option B: Primary Active Transport**:
- This type of transport directly uses ATP to move solutes against their concentration gradient. However, it does not involve coupling the transport of two different solutes, so this option is incorrect.
- **Option C: Facilitated Diffusion**:
- Facilitated diffusion is a passive transport mechanism that does not require ATP and moves solutes down their concentration gradient. This does not match the requirement of active transport against a gradient, making this option incorrect.
- **Option D: Antiport Transport**:
- Antiport transport involves the active transport of two different solutes in opposite directions. In this case, one solute is transported against its gradient while the other is transported down its gradient, which perfectly fits the description given in the question.

3. **Conclusion**:
- After analyzing all options, the correct answer is **Option D: Antiport Transport**.

### Final Answer:
The carrier-mediated cotransport in which a solute is actively transported across a membrane against the gradient of electrochemical potential by coupling the uphill transport of one solute to the downhill transport of another is an example of **Antiport Transport**.