Question

1. If an cation has an equilibrium potential of -90 mV and the membrane potential of a cell is -60 mV, activation of a channel for this cation would result in

A. no net movement of that cation.

B. efflux of that cation.

C. influx of that cation.

2. If an cation has an equilibrium potential of 50 mV and the membrane potential of a cell is -60 mV, activation of a channel for this cation would result in

A. no change in membrane potential.

B. depolarization.

C. hyperpolarization.

Answer 1

Q1) B. Efflux of that cation.

Captions are positively charged. Since inside of the cell is -60mV, to reach the equilibrium ,cations will move out so that the inside of the cell becomes equilibrium potential for the cation.

Q2) B. Depolarisation.

Since equilibrium potential of the cation is 50mV, the potential of the cell become positive due to the influx of the cation into the cell. The potential starts to rise from -60mV and becomes closer to zero and then depending on the influx of the amount of cation becomes more positive until it reaches the equilibrium 50mV. This process of reversal of cellular potential from negative to zero and then positive is know as depolarisation.