34 out of 95
Sodium-potassium-ATPase helps in the mainte-nance of which of the following?
|A||Cell surface charge|
|C||Low extracellular sodium|
|D||High extracellular potassium|
Ans. B >A
- The sodium-potassium pump is the most commonly active transport mechanism in the body.
- This pump is present in all cells in body and is responsible for maintaining the sodium and potassium concentration differences across the cell membrane as well as for establishing a negative electrical potential inside the cells.
- When 3 sodium ions bind on the inside of this carrier protein and 2 potassium ions on the outside, the ATPase function of the protein becomes activated Q.
- This then cleaves 1 molecule of ATP, splitting it to ADP and liberating a high-energy phosphate bond of energy.
- This energy is then believed to cause a conformational change in the protein carrier molecule, extruding the sodium ions to the outside and the potassium ions to the inside.
- By this process a net of 1 positive charge is moved from the interior of the cell to the exterior for each revolution of the pump.
- This creates positivity outside the cell but leaves a deficit of positive ions inside the cell; that is, it causes negativity on the inside.
- Therefore, the sodium-potassium pump is said to be electrogenic Q because it creates an electrical potential across the cell membrane as it pumps.
- One of the most important functions of the sodium-potassium pump is to control the volume of the cells. Without function of this pump, most cells of the body would swell until they burst Q.