With energy input, against the concentration, osmotic pressure, or electrical gradient, it requires transporter proteins, also called pumps.
It can only be made by some types of specialized proteins. The necessary energy is obtained from the hydrolysis of ATP , which is why these proteins are said to be ATPase.
The Na+ / K+ pump
It is the most important ionic bomb. Animal cells have a higher concentration of K+ ions in their internal environment than outside, and a higher concentration of Na+ in the extracellular environment than inside.
The differences in concentration are due to the fact that the pump, for each hydrolyzed ATP, expels three Na+ ions towards the outside and introduces two K+ ions towards the inside, against the concentration gradient .