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 function of transport proteins: Transport proteins facilitate the movement of substances across a cell membrane. They can transport molecules in the same direction or in opposite directions.
2. Define the term 'antiporter': An antiporter is a type of transport protein that moves two different molecules or ions across a membrane in opposite directions.
3. Differentiate between types of transport proteins: A uniporter transports a single type of molecule in one direction, a symporter transports two different molecules in the same direction, and an antiporter transports two different molecules in opposite directions.
4. Identify the correct term based on the description: Since the problem describes a protein that transports two different molecules in different directions, it matches the definition of an antiporter.
5. Conclude that the correct answer is 'An antiporter' based on the provided options and the definition of each type of transport protein.