Homework 4 Solutions

Homework 4 Solutions - avogadro's number of particles per...

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Question 1 We talked about this question in class: Assume a cell has radius r=10μm and membrane capacitance 1μF/cm 2 . How many uncompensated charges must cross the membrane to produce the resting membrane potential of -70 mV? Remember, in the formula Q=CV, Q is in Coulombs (6.24151×10 18 charges), C is in Farads, and V is in Volts. You can enter your answer with 3 significant digits either in scientific notation or regular notation (e.g. 3.45E+6 or 3450000). Answer 5.489E+6 Question 2 Assuming the cell from above has a concentration of K+ inside of 100mM (where 1 molar is
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Unformatted text preview: avogadro's number of particles per liter), how many total potassium ions are inside the cell? Remember there are 1000 cm 3 /liter. Answer 2.52E+11 Question 3 Assume a cell has a membrane resistance of 10,000 Ohms cm 2 and a capacitance of 1F/cm 2 . What is the time constant in ms? Answer 10 Question 4 If the membrane potential in response to a step current injection is as follows: V(t) = -30mV e-t/2ms-40mV then at what value of t will the voltage have risen 99% of the way from rest to its asymptotic value? Answer 9.21...
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