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This molecular machine works as a pump which picks up sodium from one side of a membrane (the two yellow lines) and moves it to the other side; then picks up potassium from that other side and moves it back to where there is less of it. It does this by changing its shape so the receptors for sodium and potassium also change their attractiveness to the compounds. You will learn more about this pumping function when you explore proteins!
How is this similar to the way an oil pump works? How is it different? Look again at the pictures!
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