Nernst equation transmembrane potential

Thus, a 10 1 transmembrane gradient of a single monovalent ion, say potassium, will generate a membrane potential of 58 mV. See Resting Potential Action Potential Depolarization Threshold Potential Nernst Equation Goldman Equation Patch-Clamp Technique... 

The transmembrane potential at the peak of the action potential can be predicted from the Nernst equation by substituting appropriate sodium ion concentrations for those of potassium ions. 

The difference in the transmembrane potential, of the mitochondria, between normal epithelial and carcinoma cells is at least 60 mV more negative in the latter due to the higher metabolic requirements of tumor cells [58], According to the Nernst equation, this difference would lead to a 10-fold increase in the cellular uptake of lipophilic cations [59], This is the principle for the superior accumulation of [ Tc]MIBI in tumor cells when compared to the epithelial or connective surrounding tissues. 

The above expression can be derived from the Nernst-Planck equations with the assumption that concentration does not vary with time. In addition the space dimension of Equation 22.4 is reduced to a two-compartment — cell interior and exterior — model. Thus the steady-state of Equation 22.4 teUs us that when there is no net current flow, the transmembrane potential will equal a quantity called the Nernst potential E = (RT/ZiP) ln([C]o/[C],) z, is the valence of the ion, [C,]o is the concentration of the ion on the outside, and [C,] is the concentration on the inside. Quantities such as ion mobility are effectively lumped into a nonlinear time-varying conductance (G,m hf). 

The expression of the transmembrane potential is in the same form as the Nernst equation. However, in this case the transmembrane potential is due mainly to the difference in the two surface potentials, and the diffusion potential is approximately zero. 

R and F are the gas constant and the Faraday constant, respectively, and Ciq and C 2 refer to the concentrations of the species in each of the two aqueous phases separated by the membrane with an assumption of equal values of jU in both phases. Unfortunately the nomenclature of Eqn. (5.3) can be confusing as another well known relation is also referred to as the Nernst equation. This relates the oxidation-reduction (redox) potential to the concentrations of the components of a redox couple. The redox potential is not a transmembrane electrical potential difference but is... 

Overall, measurements of transmembrane potential differences in living cells is fairly well established with the methods fairly reliable and robust. These mostly take on two strategies either utilising electrodes or optical tools such as fluorescence to record the potential differences (Vm or Ai/ ) based on electrochromism or probe accumulation according to the Nernst equation (5.3). 

The ideas of Overton are reflected in the classical solubility-diffusion model for transmembrane transport. In this model [125,126], the cell membrane and other membranes within the cell are considered as homogeneous phases with sharp boundaries. Transport phenomena are described by Fick s first law of diffusion, or, in the case of ion transport and a finite membrane potential, by the Nernst-Planck equation (see Chapter 3 of this volume). The driving force of the flux is the gradient of the (electro)chemical potential across the membrane. In the absence of electric fields, the chemical potential gradient is reduced to a concentration gradient. Since the membrane is assumed to be homogeneous, the... 

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