1. Suppose that the membrane of a neuron is permeable only to magnesium ions. Th

Question

1. Suppose that the membrane of a neuron is permeable only to magnesium ions. The ion concentrations on either side of the membrane are listed below.

[]outside []inside

Mg2+ 200 mM 20mM

K+ 5 mM 100mM

C. Is there any net flow of ions at this resting potential? Why or why not?

Suppose that you voltage clamp the cell and inject current so that it becomes hyperpolarized by 40 mV.

D. What is the new membrane potential? Explain your thinking.

E. Will there be a net flow of Mg2+ ions at the new membrane potential? Why or why not? If so, in what dir

Explanation / Answer

1) If the membrane is permeable only to magnesium ions, there will be flow of magnesium ions from outside to inside because of concentration gradient.

If the membrane hyperpolarises, there is an increase in negative charge. So, there will be a loss of magnesium ions from inside to outside of the cell.

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