They discovered this since S waves don’t travel through the earth but P waves do. P waves tend to travel faster than S waves in speed, 1&14km/s vs 1&8km/s
Sodium potassium pump is an active pump which transfer sodium and potassium ions across the membrane with the expenditure of energy in the form of ATP.
This kind of pump is generally used in nerve cells.
The pump works against the concentration gradient as the pump moves three Na+ ions outside the cell and two K+ ions inside the cell, though there is a high concentration of Na+ outside the cell and a low concentration of K+ outside the cell.
