The sodium-potassium ion exchange pump a) must reestablish ion concentrations after each action potential. b) transports sodium ions into the cell during depolarization. c) transports potassium ions out of the cell during repolarization. d) moves sodium and potassium opposite to the direction of their electrochemical gradients. e) depends on a hydrogen gradient for energy.

Moves sodium and potassium opposite to the direction of their electrochemical gradients. (Ans. D)

Explanation:

Sodium potassium pump: It is present in many plasma membrane of the cells. A protein which is present on the many cells is maintained the internal and external environment concentration by maintain internal concentration of potassium higher than outside and internal concentration of sodium lower than outside.

With the help of the ATP, moves sodium and potassium opposite to the direction of their electrochemical gradients. Two potassium ions are imported and three sodium ions are ejected in a cell, In a single pump cycle.

the correct answer is:

a population changes in response to a change in the environment.