Final answer:
The sodium-potassium pump is a form of active transport using ATP energy to move sodium and potassium ions against their concentration gradients, an example of energy coupling. After pumping, ions can return to their original locations through facilitated diffusion.
Step-by-step explanation:
The sodium-potassium pump (Na+/K+ pump) is an essential cellular mechanism and is an example of active transport. This transport mechanism utilizes ATP to move three sodium ions out of the cell and two potassium ions into the cell, thus maintaining proper concentration gradients essential for physiological processes such as nerve impulse transmission and muscle contraction. The energy to power this pump comes from the hydrolysis of ATP (an exergonic reaction), which provides the necessary free energy for the movement of these ions against their concentration gradients and electrical gradient. The energy from ATP hydrolysis is coupled with the movement of ions which illustrates the concept of energy coupling. The phosphorylation of the pump as a result of ATP hydrolysis leads to a change in the shape of the pump protein, enabling it to move ions across the membrane.
To answer the question about how ions return to their original positions: Following the pumping action, ions can move back down their concentration gradients through a process called facilitated diffusion. This is possible because the concentration gradients established by the sodium-potassium pump ensure that there is a higher concentration of sodium ions outside the cell and a higher concentration of potassium ions inside the cell, promoting their respective diffusion back and forth as needed.