Question

Describe the direction across a membrane the electrochemical gradient of sodium will move potassium, along with the chemical and electrical gradients of potassium that influence this

Answer 1

The electrochemical gradient of the membrane tend to pump K+ into the cell and Na+ out of the cell.

• Na+ -K+ ATPase is present in all eukaryotic cells.This is an antiport that pumps K+ into the cell and Na+ out of the cell against their concentration gradients.T
• This antiport transport system is primarily responsible for maintaining the high K+ and low Na+ concentration inside the cells.
• The Na+ -K+ ATPase is heterodimeric protein made up of alpha and beta subunits.
• At the cytoplasmic side the alpha subunit has ATPase activity and binding for 3Na+,ATP and phosphate.
• At the extracellular side,alpha subunit has binding sites for 2K+.
• The phospate group is bound to an aspartic acid residue of the alpha subunit.
• On activation,Na+ -K+ ATPase pumps three Na+ ions out of the cell and two K+ into the cell .Na+ -K+pump catalysed the hydrolysis of ATP to ADP,and uses this energy to pump three Na+ out of the cell and two K+ into the cell for each mole of ATP hydrolysed.
• Therefor,Na+ -K+ pump is an electrogenic pump as it forces net positive charge to out of the cell,and it has the coupling ratio of 3/2.