When transport proteins simultaneously move two molecules across a membrane in the same direction ,the process is called

Options

A. uniport
B. antiport
C. symport
D. diffusive port.

Explanation

To solve the question, "When transport proteins simultaneously move two molecules across a membrane in the same direction, the process is called," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Transport Proteins**:
- There are different types of transport proteins that facilitate the movement of molecules across cell membranes. The key types to focus on are unipot, antiport, and symport.

2. **Define Unipot**:
- Unipot transport involves the movement of a single type of molecule across the membrane in one direction. This means only one molecule is transported at a time.

3. **Define Antiport**:
- Antiport transport refers to the simultaneous movement of two different molecules across the membrane, but in opposite directions. For example, one molecule moves into the cell while another moves out.

4. **Define Symport**:
- Symport transport is when two different molecules are moved across the membrane in the same direction at the same time. This is the key definition relevant to the question.

5. **Define Diffusive Transport**:
- Diffusive transport refers to the movement of molecules from an area of high concentration to an area of low concentration, without the need for transport proteins. This process is not specific to the directionality of two molecules.

6. **Identify the Correct Answer**:
- Given the definitions, when two molecules are moved in the same direction by transport proteins, this process is specifically called **symport**.

### Conclusion:
The answer to the question is **option 3: symport**.

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