Active Transport
The energy-requiring transport of ions or molecules across a biological cell membrane against their concentration gradient.
Governing formula
3 Na⁺_out + 2 K⁺_in per ATP Hydrolyzed (Sodium-Potassium Pump)
SI unit
Ions/sec or μmol/min
In depth
Primary active transport uses direct ATP hydrolysis energy (like the Na⁺/K⁺-ATPase pump) to move ions against electrochemical gradients, establishing ion concentrations essential for secondary transport and nerve excitability.
Examples in the real world
The Na⁺/K⁺-ATPase pump consuming ~30% of resting human cellular ATP energy to maintain cell membrane potentials.