SODIUM – POTASSIUM PUMPSODIUM – POTASSIUM PUMP

Inside Cell: High K+ / Low Na+ relative to extracellular medium

The sodium potassium pump uses energy to generate and maintain these concentration gradients

Moves Na+ out, K+ in whilst hydrolysing ATP

Uses up approx. 30% cell’s energy

SODIUM – POTASSIUM PUMPSODIUM – POTASSIUM PUMP

Animation

SODIUM – POTASSIUM PUMPSODIUM – POTASSIUM PUMP

Transmembrane protein 4 subunits 2 large/ 2 small

– 3 Na+ binding sites– 2K+ binding sites– ATPase function– 1 site which is phosphorylated

3 Na+ moved out, 2 K+ moved in

Generates electrical potential inside cell (-ve)

SODIUM – POTASSIUM PUMPSODIUM – POTASSIUM PUMP Works by cyclical process flip-flopping between two

conformation Flip-flop governed by phosphorylation

3 Na+ bind on cytoplasmic surface Binding changes conformation activating ATPase ATPase phosphorylates the protein, hydrolysing ATP Causes further conformational change Moves 3Na+ to extracellular side Released because phosphorylation also reduces affinity of protein for Na+

(conformational change) 2 K+ bind on extracellular side (conformational change) Dephosphorylation occurs (conformational change) Restores original conformation Protein flips back to cytoplasmic side taking 2K+ with it 2K+ released

SODIUM – POTASSIUM PUMPSODIUM – POTASSIUM PUMP

Protein conformation change brought about by covalent modification (phosphorylation)– Changes affinity for Na+/ K+– Flips the protein’s conformation causing the

ions to be movedDephosphorylation (phosphatase) flips it

backInhibtied by ouabain

Bushman’s Poison