Which option below best describes a transporter that requires ATP to move molecules A and B out of the cell?

• A. An active antiporter.
• B. A passive antiporter.
• C. A passive symporter.
• D. An active uniporter.
• E. An active symporter.

Answer: (E)

Verified step by step guidance

1. Understand the types of transport: Active transport requires energy (usually ATP) to move substances against their concentration gradient, while passive transport does not require energy and moves substances down their concentration gradient.
2. Identify the role of ATP: Since the problem specifies that ATP is required, we are dealing with active transport.
3. Differentiate between uniporters, symporters, and antiporters: A uniporter transports one type of molecule, a symporter transports two or more molecules in the same direction, and an antiporter transports two or more molecules in opposite directions.
4. Analyze the movement of molecules A and B: The problem states that molecules A and B are moved out of the cell, which suggests they are being transported in the same direction.
5. Conclude the type of transporter: Since ATP is required and molecules A and B are moved in the same direction, the transporter is an active symporter.