Chloride (Cl-), a negatively-charged ion, is in equilibrium with regards to its

Question

Chloride (Cl-), a negatively-charged ion, is in equilibrium with regards to its flux across a membrane at a potential of -70 mV (inside of membrane negative relative to outside). (Elsewise stated, ECl = -70 mV.)

1. Describe the forces (in terms of both direction and magnitude) acting on chloride across the resting membrane. If the normally low permeability to chloride is suddenly increased, what will happen in terms of chloride flow across the membrane?

2. An experimenter alters the voltage across the membrane by passing current to make the inside -40 mV relative to the outside, and then treats the membrane in a way that briefly makes it very permeable to Cl-. What are the forces (both direction and magnitude) acting on chloride? Will chloride flow cause the voltage to change (from -40 mV), and if so, in which direction? Explain.

2a. In an experiment similar to part 2, current is passed which hyperpolarizes the membrane to -100 mV before it is made permeable to chloride. Answer the same questions as in 2 for this new experiment.

Explanation / Answer

If the equilibrium is disturbed in the membrane potential and premeability of chloride ions is increaed then it will lead to hyperpolarization of the cell. The cell's negative charge increases caused by influx of Cl-- inside the cell.

2. If inside of the cell membrane becomes less negative from (-70mV to -40mV) this leads to the electric shift called as depolarization. The sodium pump close at the peak of the action while potassium continues to leave the cell. A combination of two forces combined acts on the cell membrane : driving Na+ inside the cell, the concentration of sodium pump and the action potential of the membrane.

After depolarization, repolarization occurs meaning that will lead to maintain the equilibrium of the action potential. This will lead to influx of chloride ions inside the plasma membrane by pumps. This will make inside more nagtive and slightly shifts towards the equilibrium and maintaining th membrane potential to -70mV.

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