The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?
A)It will be on the cytoplasmic side of the ER.
B)It will be on the side facing the interior of the ER.
C)It could be facing in either direction because the orientation of proteins is scrambled in the Golgi apparatus.
D)It doesn't matter, because the pump is not active in the ER.

Question

Quizplus · Accepted Answer

The ATP binding site of the sodium-potassium pump will be on the cytoplasmic side of the ER because proteins maintain their orientation from the ER to the plasma membrane, and the ATP binding site needs to face the cytoplasm to function.

The Sodium-Potassium Pump in Animal Cells Requires Cytoplasmic ATP to Pump