Final answer:
Active transport is exemplified by the sodium-potassium pump, which uses energy from ATP to move sodium and potassium ions across the cell membrane against their concentration gradients.
Step-by-step explanation:
An example of active transport is the sodium-potassium pump, which actively moves sodium ions (Na+) out of the cell and potassium ions (K+) into the cell. This process requires energy, typically harnessed from the hydrolysis of adenosine triphosphate (ATP), to move these ions against their respective concentration gradients. The sodium-potassium pump is fundamental in maintaining the electrochemical gradient necessary for nerve impulse conduction and cellular homeostasis.