Question

which of the following causes an unequal ion concentration across the resting plasma membrane?
a the attraction of sodium ions to chloride ions
b the attraction of chloride ions to other intracellular anions
c negatively charged proteins do not readily diffuse across the plasma membrane
d the repulsion of potassium ions by the intracellular anions
e the functioning of the sodium - chloride pump

Explanation:

• Option A: Sodium and chloride ions' attraction doesn't directly cause unequal ion concentration across the resting plasma membrane.
• Option B: Chloride ions' attraction to other intracellular anions is not the main cause of the unequal ion concentration.
• Option C: Negatively - charged proteins being unable to diffuse readily across the plasma membrane contributes to the unequal ion concentration. These proteins are more concentrated inside the cell, and their inability to move out freely affects the balance of ions.
• Option D: Potassium ions are not repulsed by intracellular anions in a way that causes the major unequal ion concentration at rest.
• Option E: There is no sodium - chloride pump. The relevant pump is the sodium - potassium pump.

Answer:

C. negatively charged proteins do not readily diffuse across the plasma membrane