Question

The sodium-potassium pump moves molecules AGAINST the gradient by sending 3 sodium ions ____________ of the cell and bringing potassium ions ______________.

a. Out, In
b. In, Out
c. In, In
d. Out, Out

Answer 1

The sodium-potassium pump moves sodium ions out of the cell and potassium ions into the cell against a concentration gradient.

Step-by-step explanation:

The sodium-potassium pump moves sodium ions out of the cell and potassium ions into the cell, both against a concentration gradient, in order to maintain the proper concentrations of both.

First, three sodium ions bind with a carrier protein in the cell membrane. Then, the carrier protein receives a phosphate group from ATP. When ATP loses a phosphate group, energy is released. The carrier protein changes shape, and as it does, it pumps the three sodium ions out of the cell. At that point, two potassium ions bind to the carrier protein. The process is reversed, and the potassium ions are pumped into the cell.