Final answer:
The maintenance of sodium and potassium ion concentrations is an example of active transport, requiring energy in the form of ATP to move ions against their concentration gradient using transport proteins or pumps.
Step-by-step explanation:
The maintenance of sodium and potassium ion concentrations at the plasma membrane involves active transport. This is because ions are transported from areas of lower concentration to areas of higher concentration, which is against their concentration gradient. This process requires energy and is facilitated by proteins that function as pumps, using ATP to move the ions across the membrane. This is vital for functions such as nerve impulse transmission and muscle contraction.
Active transport mechanisms such as the sodium-potassium pump directly use energy to transport substances against their concentration gradient. Vesicle transport is another type of active transport where substances are enclosed in vesicles to be carried across the plasma membrane, requiring cellular energy.
Therefore, when considering the maintenance of sodium and potassium ion concentrations, the type of transport taking place is active transport due to the involvement of cellular energy and transport against the concentration gradient.