Nernst equation worksheet PDF

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Department of Biological sciencesXS Cell membranes Work sheet The distribution of major ions across the cell membrane of a nerve cell is as follows: Ion Extracellular Intracellular concentration concentration mM mM Na+ 150 10 K+ 5 140 Cl- 105 7 Ca++ 1 0.(a) Calculate the equilibrium potential for ea...

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Department of Biological sciences XS1200 Cell membranes Work sheet 1. The distribution of major ions across the cell membrane of a nerve cell is as follows:

Ion

Na+ K+ ClCa++ (a)

Extracellular concentration mM 150 5 105 1

Intracellular concentration mM 10 140 7 0.02

Calculate the equilibrium potential for each ion using the Nernst equation which at 20oC is:

E = 58 . log10 [Concentrationoutside] Z [Concentrationinside] Where z= valency

(b)

The membrane potential for this cell was measured as -70 mV. List TWO significant conclusions that can you draw about this observation.

(c)

Describe (no calculations are needed) the effect that each of the following situations would have on this cell’s membrane potential: (i) (ii) (iii)

an increase in the membrane permeability to K+. an increase in extracellular K+ concentration. An increase in membrane permeability to Cl-.

2. In an experiment designed to study the effects of changing external [K +] on the resting membrane potential of a cell the following results were obtained:

external potassium concentration [Ko] (mM) 1 2.5 5 10 25 50

measured membrane potential (mV) -98 -85 -75 -60 -42 -25.8

The intracellular [Ki+] remained constant throughout at 139 mM. (a)

For each external potassium concentration [Ko] calculate the expected equilbrium potential for potassium.

E (mv) =

(b)

58.log10 [Ko]  [Ki]

Briefly account for the difference between measured membrane potentials and calculated equilibrium potentials....