1) Question 1 (20 pts ) You are studying neurons in the lab by growing them in c
ID: 132374 • Letter: 1
Question
1)Question 1 (20 pts) You are studying neurons in the lab by growing them in culture (in a petri dish outside the body). You grow them in an incubator at 37 degrees C. With this experimental setup, you can easily change the extracellular ion concentrations by switching the cell culture medium (the fluid that surrounds the cells).
Intracellular concentration
Medium 1 (extracellular concentration)
Medium 2 (extracellular concentration)
K+
140 mM
4.5 mM
50 mM
Na+
10 mM
135 mM
100 mM
Cl-
12 mM
125 mM
120 mM
In which media is the resting potential of the cell more depolarized? Assume the relative permeabilities of the ions are 100, 1, and 5 for K, Na, and Cl. Show your work.
Intracellular concentration
Medium 1 (extracellular concentration)
Medium 2 (extracellular concentration)
K+
140 mM
4.5 mM
50 mM
Na+
10 mM
135 mM
100 mM
Cl-
12 mM
125 mM
120 mM
Explanation / Answer
Depolarization is defined as loss of polarisation. It is the loss of charge between the inside and outside of the cell. Depolarisation occurs mainly due to increase in permeability of ionic channels. The relative permeabilities of the ions are 100, 1 and 5 for K, Na and Cl respectively. Applying the relative permeability factor, the charge of ions intracellularly is +139.5. In medium 1 it is -0.4 and in medium 2 it is +45. So, in medium 1, the resting potential of the cell is more depolarized.
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