You Answered Question 22 0 / 3 pts Calculate the membrane potential when intracellular [Ca2+] = 0.876 mM and extracellular [Ca2+] = 3.0 mM at 37°C, with a AG of -4,960 J/mol. 42 mV -19 mV 84 mV Correct Answer -9.3 mV

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 Ohms law: Ix=Gx(VmEx) which describes the movement of ion x across the membrane. I is the current in amperes (A); G is the conductance, a measure of the permeability of x, in Siemens (S), which is I/V;Vm is the membrane voltage; and Ex is the equilibrium potential of ion x. Not only does this equation tell how large the current is, but it also tells what direction the current is flowing. By convention, a negative value of the current represents either a positive ion entering the cell or a negative ion leaving the cell. The opposite is true of a positive value of the current. a. Using the following information, calculate the magnitude of Na [ Na+ ]0=145mM,[ Na+ ]i=15mM,Gna+=1nS,Vm=70mV b. Is Na+ entering or leaving the cell? c. Is Na+ moving with or against the concentration gradient? Is it moving with or against the electrical gradient?

Calculate 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/mol

ommand Resting membrane potential - Data oloiezd & vmotnA concentration (mM) Membrane Voltage (mV) K+ inside K+ outside Na+ inside Na+ outside 140 140 4. -68-036 mV MIDO 140 00 140 4 Questions 1. What was the effect of increasing extracellular K+ to 100 mM on the membrane's potential? 2. Explain why the above change occurred.