Concept explainers
One of the important uses of the Nernst equation is in describing the flow of ions across plasma membranes. Ions move under the influence of two forces: the concentration gradient (given in electrical units by the Nernst equation) and the electrical gradient (given by the membrane voltage). This is summarized by Ohm’s law:
a. Using the following information, calculate the magnitude of ‘Na
b. Is
c. Is
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Human Physiology: From Cells to Systems (MindTap Course List)
- Describe the contribution of each of the following to establishing and maintaining membrane potential: (a) the Na+K+ pump, (b) passive movement of K+ across the membrane, (c) passive movement of Na+ across the membrane, and (d) the large intracellular anions.arrow_forwardV=62 log 10 (C0/Ci ) for a positive ion at 37 degrees Celsius. What is theoretical ratio of solution ion across the membrane when the resting membrane potential is 124 mV?arrow_forwardBelow find the structures for ibogaine and cocaine. Ibogaine and cocaine inhibit the dopamine active transporter (DAT). This transporter is a secondary active transporter, and depends on the primary active transporter Na+/K+ ATPase. Ibogaine had a Kι = 2 μM, and cocaine a Kι = 0.64 μM respectively. (a) Define secondary active transport. (b) Is ibogaine an effective treatment for cocaine based on DAT binding?arrow_forward
- 1. (a) In class thus far, we have focused our membrane transport energetics discussions on the transfer of K+ ions. Of course, in the cell there are other ions that contribute to the overall resting membrane potential (Autotal). To estimate the overall resting membrane potential for the predominant ions present in the cell, we must first calculate the individual resting membrane potential. Using the Nernst equation discussed in class, and the values provided below, calculate A for each ion. lon K+ Na+ Ca²+ CI- [ion] outside cell 6 mM 145 mM 4 mM 90 mM [ion] inside cell 145mM 8 mM 0.001 mM 6 mMarrow_forwardFor a typical vertebrate cell with a membrane potential of −0.070 V (inside negative), what is the free-energy change for transporting 1 mol of Na+ from the cell into the blood at 37 °C? Assume the concentration of Na+ insidethe cell is 12 mM and in blood plasma it is 145 mM.arrow_forwardUse the Goldman Equation to calculate the resting membrane potential at 37°C for each case:arrow_forward
- For most neurons, the extracellular concentration of chloride ions (Cl-) is 108 mM, whilethe intracellular concentration of Cl- is 5 mM.If the plasma membrane becomes more permeable to Cl-, would there be Clinflux or Cl- efflux at an RMP of -70 mV? Why?arrow_forwardIn the Nernst equation [V = 62 log10 (Co/ Ci)], the term Co represents: the intracellular concentration of calcium the extracellular concentration of potassium the extracellular concentration of sodium the intracellular concentration of potassium the membrane potential (in millivolts)arrow_forwardCalculate the change in Gibbs free energy for transport of Ca2+ from outside to inside the cell. The extracellular Ca2+ concentration is 135 uM, and the intracellular Ca2+ concentration is 98 uM. The membrane potential is -22 mV and the temperature is 37°C. O. -5.1 kJ/mol O 1.2 kJ/mol -410 kJ/mol 3.4 kJ/molarrow_forward
- Chloride ions (Cl-) behave a bit differently to Na+ and K+ in that most cells don't have active Cl- transporters. As a result, the concentration gradient for Cl- is not 'set' like it is for Na+ and K+. There are, however, a limited number of Cl- leak channels in the cell membrane. As a result, Eci generally matches resting membrane potential - around - 70mV. Considering this, answer the following questions. If Cl- can cross the cell membrane, is not being actively transported, and membrane potential is -70mV, will there be a concentration gradient for Cl-?arrow_forward7. Given the following concentrations: K* ICF 140 mM Na CH 12 mM 12 mM ECF 3 mM 145 mM 120 mM a) Calculate the equilibrium potentials of K, Na* and Cl using the Nernst equation. EK = ENa = ECi = b) In the case above, if the membrane is permeable only to K, what would be the predicted membrane potential? c) If the membrane is equally permeable to K and Na", and impermeable to all other ions, what would be the predicted membrane potential?arrow_forwardIn the situations described below, what is the free energy change if 1 mole of Na+ is transported across a membrane from a region where the concentration is 48 μM to a region where it is 110 mM? (Assume T=37∘C.) When the transport is opposed by a membrane potential of 70 mV.arrow_forward
- Human Physiology: From Cells to Systems (MindTap ...BiologyISBN:9781285866932Author:Lauralee SherwoodPublisher:Cengage Learning