SODIUM

1
(No Transcript)
2
(No Transcript)
3
SODIUM 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 cells energy

4
SODIUM POTASSIUM PUMP

• Animation

5
SODIUM 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)

6
SODIUM 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

7
SODIUM POTASSIUM PUMP

• Protein conformation change brought about by
  covalent modification (phosphorylation)
• Changes affinity for Na/ K
• Flips the proteins conformation causing the ions
  to be moved
• Dephosphorylation (phosphatase) flips it back
• Inhibtied by ouabain

8
(No Transcript)