Which of the following ions is most likely to cross the plasma membrane of a resting neuron?

Question

Quizplus · Accepted Answer

K⁺ is the ion that is most likely to cross the plasma membrane of a resting neuron because most neurons maintain a higher concentration of K⁺ ions inside the cell compared to the extracellular fluid. This concentration gradient allows K⁺ to move passively out of the cell through K⁺ leak channels in the plasma membrane, which contributes to the resting membrane potential of the neuron. The other ions listed (Na⁺, Ca²⁺, Cl⁻, and Mg²⁺) are either present at much lower concentrations inside the cell or are actively transported across the membrane, making them less likely to cross the plasma membrane at rest.

Which of the Following Ions Is Most Likely to Cross