Final answer:
Potassium (K+) ions are shifted into cells by the sodium-potassium pump, which exchanges three Na+ ions for two K+ ions using ATP, the activity of potassium binding proteins, and hormonal influences such as aldosterone, aiding in the regulation of extracellular K+ concentration.
Step-by-step explanation:
The factors that shift potassium ions (K+) into cells, thus decreasing extracellular [K+], include the activity of the sodium-potassium pump, which moves three sodium ions (Na+) out of the cell and two K+ ions into the cell against their concentration gradients. This process utilizes ATP, and for each ATP molecule consumed, a net decrease of one cation occurs inside the cell, maintaining a negative intracellular charge relative to the extracellular fluid.
The presence of potassium binding proteins and other negatively charged molecules inside the cell further helps to maintain a high intracellular K+ concentration. Hormonal regulation such as the action of aldosterone influences the exchange of Na+ and K+ in the renal tubules, which indirectly affects K+ balance by influencing the sodium-potassium pump operation and K+ excretion or retention by the kidneys.