The sodium-potassium ATPase pump is an essential protein found in the cell membrane of animal cells. It helps maintain the proper balance of sodium and potassium ions inside and outside the cell. Here are the steps involved in the functioning of the sodium-potassium ATPase pump:
1. The pump starts with three sodium ions (Na+) binding to the cytoplasmic side of the protein. This causes ATP (adenosine triphosphate) to bind to the protein as well.
2. The ATP molecule is then hydrolyzed, meaning it is broken down into ADP (adenosine diphosphate) and inorganic phosphate (Pi). This process releases energy that is used to change the shape of the protein.
3. As the shape of the protein changes, it exposes the sodium ions to the outside of the cell. This causes the sodium ions to be released into the extracellular fluid.
4. At the same time, the shape change of the protein allows two potassium ions (K+) from the extracellular fluid to bind to the protein on the outside of the cell.
5. The binding of the potassium ions triggers the release of the inorganic phosphate (Pi) from the protein, and this causes the protein to return to its original shape.
6. The return to the original shape of the protein allows the potassium ions to be released into the cytoplasm of the cell.
7. The pump is now ready to start the cycle again, with the binding of three sodium ions and one ATP molecule.
In summary, the steps of the sodium-potassium ATPase pump involve the binding of sodium ions on the cytoplasmic side, the hydrolysis of ATP to release energy and change the shape of the protein, the release of sodium ions to the extracellular fluid, the binding of potassium ions from the extracellular fluid, the release of inorganic phosphate to return the protein to its original shape, and the release of potassium ions into the cytoplasm of the cell. This process helps maintain the proper balance of sodium and potassium ions inside and outside the cell.