Question

Consider a nerve cell with an internal Cl- concentration of 50 mM, a membrane potential of 60 mV and an external Cl- concentration of 100 mM. Each of the following is true for Cl- import into the cell except

A) import is down a concentration gradient.
B) import is down an electrochemical concentration gradient.
C) import ΔG is positive.
D) import requires energy input.
E) All are true.

Answer 1

Cl- import into the cell is energetically favorable, as it goes down its concentration and electrochemical gradients, and thus does not require energy input. Statement D is incorrect for the given scenario.

Step-by-step explanation:

The student's question pertains to whether or not chloride ion (Cl-) import into a nerve cell is energetically favorable or requires energy input, given a set of membrane potential and concentration gradients.

The correct statement is that Cl- import into the cell is down the concentration gradient (from higher to lower concentration) and down the electrochemical gradient.

However, the import ΔG (change in Gibbs free energy) would not be positive as the ion is moving down its electrochemical gradient, implying an energetically favorable process.

Hence, it does not necessarily require energy input. So the statement 'import requires energy input' (D) is the one that does not hold true in this scenario.