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In doing so, it pumps the three sodium ions out of the cell. At that point, two potassium ions from outside the cell bind to the protein pump. The potassium ions are then transported into the cell, and the process repeats. The sodium-potassium pump is found in the plasma membrane of almost every human cell and is common to all cellular life.
It helps maintain cell potential and regulates cellular volume. The active transport of ions across the membrane causes an electrical gradient to build up across the plasma membrane. The number of positively charged ions outside the cell is greater than the number of positively charged ions in the cytosol.
This results in a relatively negative charge on the inside of the membrane, and a positive charge on the outside. This difference in charges causes a voltage across the membrane.
Voltage is electrical potential energy that is caused by a separation of opposite charges, in this case across the membrane. The voltage across a membrane is called membrane potential. Membrane potential is very important for the conduction of electrical impulses along nerve cells. Because the inside of the cell is negative compared to outside the cell, the membrane potential favors the movement of positively charged ions cations into the cell, and the movement of negative ions anions out of the cell.
These two forces working together are called an electrochemical gradient , and will be discussed in detail in "Nerve Cells" and " Nerve Impulses " concepts. The Sodium-Potassium Pump Active transport is the energy-requiring process of pumping molecules and ions across membranes "uphill" - against a concentration gradient.
The Electrochemical Gradient The active transport of ions across the membrane causes an electrical gradient to build up across the plasma membrane. Summary Active transport is the energy-requiring process of pumping molecules and ions across membranes against a concentration gradient. The sodium-potassium pump is an active transport pump that exchanges sodium ions for potassium ions.
Explore More Use this resource to answer the questions that follow. Are there more sodium ions on the outside of cells or the inside?
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