Question
(Passage-based question, MCAT style) In a neural cell, the transmembrane potential is negative in the absence of neural impulse. During the propagation of the neural impulse the "action potential"), the transmembrane is siga mostly due to influx of Na .Considering given extra- and intracellular potential changes of Na and K Table in the problem 9) in a neuron with the initial transmembrane potential of 60 mV potential inside the cell is lower than outside). circle or underline the comect answer in parentheses (real passage carefully and have In the absence of the action potential. L Transmembrase potential is close no Na+, K+. both ions equilibrium potential. This aueaas (Na K boch) channels are closed II. The Gibb's free energy for transfeming one mole of Na ioesiatothe cell would be positive, negative, meaning suc transfer (can, caano) occur channels are As the action poteauial develops, IIL (Na .K both) channels open and the membrane potential becomes closer to the equilibrium potential for (Na ,K .both). concemaation of the ices iaside and outside the cell (can, cannot be restored spontaneoudy.
Explanation / Answer
The answers will be
I) the transmittance potential will be close to both the ions equilibrium potential which means that both channels are closed
II) The Gibbs free energy for transfering one mole of Na+ into the cell would be negative meaning such transfer can occur spontaneously if Na+ channels are open.
III) K+ channels open and the membrane potenital becomes closer to equilibrium potential for Na+
IV) the initial concentration cannot be restored spontaneously
