Meet Na+/K+ ATPase!

Its name is pronounced “sodium-potassium A. T. P. ay-ss” but it more commonly goes by “sodium-potassium pump” or “Na+/K+ pump.” It works at the cell membrane and is named for its job: pumping sodium and potassium ions using energy from ATP.

Animal cell with the plasma membrane colored pink.
Animal cell

The amounts of these positively-charged ions in the cell needs to stay at a safe level. Extreme changes in the cell’s net charge can stop other proteins from doing their jobs and cause damage. So, Na+/K+ pump is critical for maintaining a proper net charge inside and outside of the cell.

Diagram showing one happy cell with a healthy net charge and two sad cells, one that is too positive and one that is too negative.
Cells need the right net charge to stay healthy.

Na+/K+ pump is a double-tasker; it pumps sodium ions out of the cell and pumps potassium ions into the cell at the same time. However, Na+/K+ pump is a bit better at the first task than the second. For every 3 sodium ions that it pumps out, it only pumps 2 potassium ions in. Both sodium and potassium ions have a +1 charge, so ultimately, the result is a net loss of +1. In other words, each time Na+/K+ pump works, the net charge in the cell becomes one unit more negative.

Diagram showing Na+/K+ ATPase in the cell membrane pumping 3 sodium ions out of the cell and 2 potassium ions into the cell.
Na+/K+ ATPase pumps sodium ions out of the cell and potassium ions into the cell.

Na+/K+ pump is made of three different parts that total approximately 1305 amino acids (protein building blocks). The biggest part, called α, moves all of the ions to their places. Moving ions requires energy, and α gathers the energy it needs from ATP (that’s why it is called an ATPase).

Three-dimensional structure model of Na+/K+ pump. Two pumps are shown mirroring each other. Energy is collected at the top, which sticks inside of the cell. Potassium ions are located within the pump. A region of helices span the membrane, and the region at the bottom sticks out of the membrane to the outside of the cell.

Na+/K+ pump moves sodium and potassium ions by swapping back and forth between two different shapes. In one shape, Na+/K+ pump is open to the inside of the cell, where it gathers sodium ions. It uses the energy it gathered to flip to another shape which opens toward the outside of the cell, where it releases sodium ions and gathers potassium ions.

Diagram showing two forms of Na+/K+ ATPase. On the left, sodium ions are exiting the pump and potassium ions are entering. On the right, potassium ions are exiting the pump and sodium ions are entering.
Na+/K+ ATPase changes shapes to pump sodium ions out and potassium ions in.

One place where Na+/K+ pump is especially important is in your nervous system. When one of your nerve cells gets a message, sodium ions flood into the nerve cell. Your nerve cell responds by relaying the message to a muscle or another nerve cell. Then, Na+/K+ pump re-sets the nerve cell by pumping the sodium back out, getting it ready to receive a new message. So, you should thank Na+/K+ pump for your ability to… well, do anything! 

If you want to learn more about Na+/K+ pump’s critical role in your nervous system, I recommend this video:  The Nervous System, Part 2 – Action! Potential!: Crash Course A&P #9

For a superdy-duper detailed description of Na+/K+ pump’s structure, visit:  https://sites.chem.utoronto.ca/chemistry/coursenotes/GTM/JM/NaKpump/start.htm#:~:text=The%20protein%20consists%20of%20three,and%20is%20the%20largest%20one.

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