Biology, Eighth Edition (Raven)

Chapter 5: Membranes

Sodium-Potassium Exchange Pump

What is the purpose of pumping sodium and potassium across a membrane? The sodium potassium pump is a well understood example of active transport. Sodium and potassium ions are pumped in opposite directions across the membrane building up a chemical and electrical gradient for each. These gradients can be used to drive other transport processes. In nerve cells the pump is used to generate gradients of both sodium and potassium ions. These gradients are used to propagate electrical signals that travel along nerves. Therefore the action of nervous tissue requires ATP to generate resting potentials. Poisons that disable the pump prevent proper functioning of the nervous system.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

The sodium-potassium pump functions to pump
A)sodium ions out of the cell and potassium ions into the cell.
B)sodium ions into the cell and potassium ions out of the cell.
C)sodium and potassium ions into the cell.
D)sodium and potassium ions out of the cell.
E)sodium and potassium ions in both directions across the cell membrane.
2.

What is the source of energy used to power the sodium-potassium pump?
A)breakdown of ATP
B)formation of ATP
C)transport of ATP by the pump
D)breakdown of GTP
E)transport of GTP by the pump
3.

During one cycle, the sodium-potassium pump binds and moves.
A)1 Na+ and 2 K+.
B)2 Na+ and 2 K+.
C)2 Na+ and 3 K+.
D)3 Na+ and 2 K+.
E)3 Na+ and 3 K+.
4.

The sodium-potassium pump is a trans-membrane protein.
A)True
B)False
5.

The binding and release of sodium or potassium ions are due to conformational changes in the protein.
A)True
B)False
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