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 concept of transport proteins: Transport proteins are integral membrane proteins that facilitate the movement of ions, small molecules, or macromolecules across a biological membrane.
2. Differentiate between types of transport proteins: Uniporters transport a single type of molecule across the membrane, symporters transport two different molecules in the same direction, and antiporters transport two different molecules in opposite directions.
3. Identify the function of an antiporter: An antiporter is a type of transport protein that moves two different molecules or ions across a membrane in opposite directions. This is often used to maintain concentration gradients and balance within cells.
4. Consider the context of the problem: The question asks for a transport protein that simultaneously transports two different molecules in different directions, which matches the definition of an antiporter.
5. Review the options provided: Compare the definitions of uniporter, symporter, equilibrium protein, and simple diffuser to confirm that antiporter is the correct choice for the described function.