Question

Which statement below best explains why ion movement through channels generates a membrane potential but ion movement generated by the Na⁺/K⁺ pump does not?

1. The concentration of K⁺ is higher inside the cell, while the concentration of Na⁺ is higher outside.
2. The slow action of the pump creates a small change in the membrane potential.
3. Ions move rapidly through ion channels, specialized pores in the membrane that allow ions to diffuse back and forth, carrying charge.
4. The net movement of positive or negative charge generates a membrane potential.
5. The Na⁺/K⁺ pump carries ions against their concentration gradients.

Answer 1

Statement second is explain the membreane pottential simply,

A membrane potential arises when there is a difference in the electrical charge on the two sides of a membrane, due to a slight excess of positive ions over negative ones on one side and a slight deficit on the other.

A good example is K+. The membrane is very permeable to K+ and the [K+] inside the cell is great, therefore a positive charge is flowing out of the cell along with K+. The [K+] inside the cell decreases causing the concentration gradient to flow towards the outside of the cell. This also causes the inside of the cell to become more electronegative increasing its electrical gradient.