An E. coli cell at maintains a membrane potential (inside minus outside) and a…

PHYSICS · Multi-part · Fermi University Physics · Biophysics & Medical Physics · Molecular machines, transport and bioenergetics · Molecular machines, transport and bioenergetics

Forces, Machines and Signals, Ch Proton gradients, ATP synthesis and photosynthesis

Problem

An E. coli cell at 310 K310\,\mathrm{K} maintains a membrane potential Δψ=−120 mV\Delta\psi = -120\,\mathrm{mV} (inside minus outside) and a cytoplasm that is 0.50.5 pH units more alkaline than the external medium. ((a)) Calculate the proton-motive force Δp\Delta p in millivolts, stating in words which way it drives protons. ((b)) Express its magnitude in kBTk_BT per proton (take kBT/e=26.7 mVk_BT/e = 26.7\,\mathrm{mV} at 310 K310\,\mathrm{K}).

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