A transport protein that simultaneously transports two different molecules in different directions is called:

• A. A uniporter.
• B. A symporter.
• C. An equilibrium protein.
• D. An antiporter.
• E. A simple diffuser.

Answer: (D)

Verified step by step guidance

1. Understand the types of transport proteins: Transport proteins facilitate the movement of molecules across the cell membrane. They can be classified based on the direction and number of molecules they transport.
2. Define a uniporter: A uniporter transports a single type of molecule across the membrane in one direction.
3. Define a symporter: A symporter transports two different molecules in the same direction across the membrane.
4. Define an antiporter: An antiporter transports two different molecules in opposite directions across the membrane. This is the key characteristic that matches the problem statement.
5. Identify the correct term: Based on the definitions, the transport protein described in the problem is an antiporter, as it moves two different molecules in different directions.