Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true?

• A. Active transport can use ATP as its energy source and ensures that there is no voltage across the cell membrane.
• B. Active transport moves solutes down their concentration gradients and always uses ATP as the source of energy to do this.
• C. Active transport uses channel proteins and ensures that the interior of the cell is always positive compared to the exterior of the cell.
• D. The source of energy for active transport of a solute up its gradient can be ATP or a concentration gradient of a second solute. This second gradient of solutes maintains no net difference in voltage across the membrane.
• E. The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane.

Answer: (E)

Verified step by step guidance

1. Understand that active transport is a process that moves molecules across a cell membrane against their concentration gradient, which requires energy input.
2. Recognize that ATP (adenosine triphosphate) is a common energy source for active transport processes, such as the sodium-potassium pump.
3. Identify that the sodium-potassium pump is an example of active transport that moves sodium ions out of the cell and potassium ions into the cell, using ATP as an energy source.
4. Acknowledge that the sodium-potassium pump creates an electrochemical gradient, resulting in a net positive charge outside the cell membrane, contributing to the membrane potential.
5. Conclude that the correct statement is that the sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane, which aligns with the principles of active transport and membrane potential.