Final answer:
Active transport is the energy-demanding process by which cells pump molecules and ions against their concentration gradient, primarily using ATP as the energy source, with carrier proteins or 'pumps' like the sodium-potassium pump to aid in this process.
Step-by-step explanation:
The type of transport involving the pumping of molecules against their concentration gradient is known as active transport. This form of transport requires additional energy to move molecules from an area of low concentration to one of high concentration—essentially moving them 'uphill'. The most common source of energy for this process is ATP (adenosine triphosphate), which cells produce mainly through cellular respiration. During active transport, carrier proteins, often referred to as pumps, are utilized to move substances against their gradient.
An example of an active transport mechanism is the sodium-potassium pump, which exchanges sodium ions for potassium ions across the plasma membrane of animal cells. This process is crucial for maintaining proper concentration gradients across the cell membrane, contributing to vital cell functions and maintaining homeostasis within the organism.