1. Gradients of ons and charged speies on either side of the cell membrane are r
ID: 3509385 • Letter: 1
Question
1. Gradients of ons and charged speies on either side of the cell membrane are responsible for many cells having a membrane potential. These electrochemical gradients are responsible for the propagation of cellular events, including action potentials. The table below lists intacelular and extracellular ion concentrations for three different ionic species, Na (Sodium), K (Potassium), and C (Chloride Na* K* Ch 10 142 140 103 FIGURE 1. Table of Intracellular and Extracellular Ion Concentrations (a) One way to determine the membrane potential across cells due to a single ionic species is the Nernst equation: where V is the membrane potential, T is the temperature, R is the ideal gas constant, z is the charge of the ionic species X], and F is Faraday's costant. Under physiological conditions, the Nernst equation can be rewritten as follows: 58Xextaar Vin =-log (intracellular In this equation, the membrane potential V is in milliVolts (mV) (a) Utilizing the values in the table above, what is the membrane potential due to Na ? (b) Utilizing the values in the table above, what is the membrane potential due to C (Hirt: What is the charge of Chloride?) (c)To get the total membrane potential due to all ions present, it is necessary to use the Goldman-Hodkin-Katz Equation, shown below: where Xo corresponds with the extracellular concentration, X corresponds with the intracellular concentra- tion, and Px corresponds with the relative permeability of ionic species X. Under physiological conditions, this simplifies to: Utilizing this equation and all the values in Table 1, what is the resting membrane potential of the cell, assuming that the K+ is 100 times more permeable than the other ions, and Na+ and Cl- have relatively equal permeability.Explanation / Answer
The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane is called NERNST POTENTIAL for that ion.
Nernst equation can be used to calculate the Nernst potential for any equivalent ion at normal body temperature of 98.6 F(37 C)
EMF(mv) =+-61 log concentration in/concentration out where EMF is electromotive force
According to the given values from the equation the equilibrium potentials (V eq) of
Na +70.91 mv
K - 95.02 mv
Cl - 86.82 mv
Electromotive driving Force
Na 142.35mv
K 23.58 mv
Cl 15.38 mv
Membrane potential is calculated from the formula
VDF (driving force) = V m( membrane potential) - V eq( equilibrium potential)
so now membrane potential is calcualted
Utilizing the values membrane potential of Na is +213. 26mv after applying intracellular concentration and extracellular concentration in the nernst equation
Vm= +213.26mv charge is positive
The driving force acting on this positively charged ion leads to its efflux from the cell ( i. e movement of the cell across the plasma membrane)
B. Utilizing the values membrane potential and charge of Cl- after applying intracellular and extracellular concentration in the nernst equation
Vm = -102.20mv charge of chloride is negative
The driving force acting on this negatively charge ion leads to its influx into the cell
C. To get total membrane potential due to all ions, Goldman Hodgkin Katz equation
Vm is calculated as
Pk 1
Pna 0.05
Pcl 0.45
And the values in the table for each ion both intracellular and extracellular calculated with the above equation as - 71.43 mv
When a nerve or muscle cell is at rest the membrane potential is called the resting membrane potential. The minus sign here indicate that the inside of the cell is negative with respect to surrounding extracellular fluid. It is determined by the concentrations of the ions in the fluids on both sides of the cell membrane and ion transport proteins that are in the cell membrane.
Assuming potassium is 100 times more permeable than the other ions and sodium and chloride are equally permeable total membrane potential due to all ions present is calculated by the Goldman equation and the resting membrane potential derived
The resting membrane potential of the cell is - 70 mv
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.