In passive transport across a membrane, when two protein molecules move in opposite direction it is called as

Options

A. uniport
B. antiport
C. symport
D. co-port.

Answer

To solve the question regarding passive transport across a membrane, we need to understand the different types of transport mechanisms that can occur. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand Passive Transport
Passive transport is a process where molecules move across a membrane without the use of energy (ATP). This movement occurs along the concentration gradient, meaning substances move from an area of higher concentration to an area of lower concentration.

**Hint:** Remember that passive transport does not require energy input.

### Step 2: Identify Types of Transport
There are different types of transport mechanisms:
- **Uniport:** Movement of a single type of molecule in one direction.
- **Symport:** Movement of two different molecules in the same direction.
- **Antiport:** Movement of two different molecules in opposite directions.

**Hint:** Think about the direction of movement for the molecules to differentiate between uniport, symport, and antiport.

### Step 3: Analyze the Question
The question specifically asks about the scenario where two protein molecules move in opposite directions across a membrane.

**Hint:** Focus on the terms "opposite direction" to narrow down the options.

### Step 4: Match the Definition to the Options
From the definitions:
- **Uniprot:** Not applicable as it involves only one molecule.
- **Symport:** Not applicable as it involves movement in the same direction.
- **Antiprot:** This matches our requirement of two molecules moving in opposite directions.
- **Copot:** This is not a standard term used in transport mechanisms.

**Hint:** Eliminate options that do not match the criteria given in the question.

### Step 5: Conclusion
Based on the analysis, when two protein molecules move in opposite directions across a membrane, it is referred to as **antiport**.

**Final Answer:** The correct answer is **option 2: antiport**.