[Campbell Biology P.187] Based on the information provided, what is the net charge transfer ... | Practice Question

Based on the information provided, what is the net charge transfer across the membrane during one complete cycle of the sodium-potassium pump, and how does it contribute to the membrane potential?

  • A: Two positive charges out; contributes to depolarization.
  • B: One positive charge in; contributes to maintaining membrane potential.
  • C: One positive charge out; contributes to maintaining membrane potential by making the inside more negative.
  • D: Three positive charges out; contributes to repolarization.

Explanation

The sodium-potassium pump actively transports three sodium ions Na+ out of the cell and two potassium ions K+ into the cell. This results in a net transfer of one positive charge out of the cell 3 positive out - 2 positive in = 1 net positive out . This differential movement of charge contributes to the negativity inside the cell relative to the outside, thus maintaining the membrane potential and acting as an electrogenic pump.