Final answer:
Active transport is a process that moves substances against their concentration gradient, requiring the use of carrier proteins and energy from ATP. An example of active transport is the sodium-potassium pump.
Step-by-step explanation:
In active transport, a carrier protein is used to move substances against their concentration gradient. ATP supplies the energy for most active transport processes. One example of active transport is the sodium-potassium pump, which exchanges sodium ions for potassium ions across the plasma membrane of animal cells.