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 symporters and antiporters: Symporters move two or more molecules in the same direction across a membrane, while antiporters move molecules in opposite directions.
4. Consider the direction of movement: The problem states that molecules A and B are moved out of the cell, which suggests they are being moved in the same direction.
5. Conclude the type of transporter: Since ATP is required and the molecules are moved in the same direction, the transporter is an active symporter, not an antiporter or uniporter.