Question

In the experiment set up below, side 1 contains 10mM KCl and 1mM NaCl, and side 2 contains 1mM KCl and 10mM NaCl. The membrane is permeable to both K+ and Na+. Please state the direction of ion flow for each ion separately under each condition at room temperature.

a) -78mV is applied to side 1

b) 58 mV is applied to side 1

c) zero (0) mV is applied

c. In the experiment set up below, side 1 contains 10mM KCl and 1mM NaCl, and side 2 contains 1mM KCl and 10mm NaCl. The membrane is permeable to both K+ and Nat. Please state the direction of ion flow for each ion separately under each condition at room temperature. battery 10mM KCL / ImM KCI IMM Nach 10mm Nach pemide to both k and Nat A) -78mV is applied to side 1 B) 58 mV is applied to side 1 C) Zero (0) mV is applied.

Answer 1

The movement of ions depend upon both, the concentration gradient and the electrical gradient due to the applied voltage

-78mV is applied to side 1: Due to the applied voltage, electrical gradient develops, but in case of negative value, the gradient is in opposite direction of that of a concentration gradient, which means KCl will move from lower to higher concentration (side 2 to 1), but NaCl will flow in concentration gradient, hence from side 2 to 1.

58mV is applied to side 1: For a positive value of the applied voltage, the gradient for NaCl reverses to that of the concentration gradient, so when the voltage is  applied on side 1, 10 mM KCl from side 1 will move to the side 2, but there will be no flow of NaCl.

zero (0) mV is applied: When no voltage is applied, the ions will move along the concentration gradient, from higher to lower, meaning that KCl from side 1 to 2 and NaCl from side 2 to 1.