Base your answers to the questions below on the following information:
A cell biologist interested in the transport of calcium ions (Ca2+)across the plasma membrane of bacterial cells made the following measurements on bacterial cells at 25°C:
Vm = - 150 mV [Ca2+] inside = 20 mM [Ca2+] outside = 0.4 mM
-Assuming no change in either the internal or external calcium ion concentration, at what membrane potential would there be no net movement of calcium across the membrane?

Question

Quizplus · Accepted Answer

The Nernst equation can be used to calculate the membrane potential at which there is no net movement of calcium ions across the membrane:Vm = (RT/zF) * ln([Ca2+]outside/[Ca2+]inside)where:Vm is the membrane potentialR is the ideal gas constant (8.314 J/mol*K)T is the temperature in Kelvin (25°C = 298 K)z is the valence of the ion (+2 for calcium ions)F is the Faraday constant (96,485 C/mol)[Ca2+]outside is the concentration of calcium ions outside the cell (0.4 mM)[Ca2+]inside is the concentration of calcium ions inside the cell (20 mM)Plugging these values into the equation, we get:Vm = (8.314 J/mol*K * 298 K) / (2 * 96,485 C/mol) * ln(0.4 mM / 20 mM)Vm = -50 mVTherefore, the membrane potential at which there would be no net movement of calcium across the membrane is -50 mV.

Base Your Answers to the Questions Below on the Following