Question

Which ion(s) have a net chemical force acting to move the ion(s) into the cell? (Assume a resting

membrane potential (Vm) of -70mV.)
A) X+, whose [ECF] is 120 mM and [ICF] is 30 mM
B) A-, whose [ECF] is 100 mM and [ICF] is 100 mM
C) B-, whose [ECF] is 140 mM and [ICF] is 30 mM
D) both X+ and B- ions
E) X+, A-, and B- ions

Answer 1

At a resting membrane potential of -70 mV, the positively charged X+ ion, with a higher concentration outside the cell, is the only ion with a net force driving it into the cell due to both electrical attraction to negative inside and its concentration gradient.

Step-by-step explanation:

The cell's resting membrane potential, typically at -70 mV, means the interior of the cell is negatively charged relative to the outside. This electrical difference drives the movement of ions due to both a chemical force (concentration gradient of the ions) and an electrical force (membrane potential). In this scenario with a resting membrane potential of -70 mV:

• X+, with a higher concentration outside the cell, will be driven into the cell both by the chemical concentration gradient (from high to low concentration) and the electrical gradient (positive ions attracted to the negatively charged interior).
• A-, with equal concentrations inside and outside will not be driven by a chemical gradient but will be repelled by the negative interior, thus, no net force to enter the cell.
• B-, with a higher concentration outside will also be repelled by the negative interior, no chemical force to enter since the concentrations are equal.

The correct answer is therefore X+, since it is the only ion with a net force acting to move it into the cell due to the resting membrane potential and its concentration gradient.