(1) You are enjoying your first co-op at a very prestigious lab at Harvard Unive
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Question
(1) You are enjoying your first co-op at a very prestigious lab at Harvard University. One day, your boss comes in with very exciting news! Colleagues of hers in Brazil have discovered a new species of frog in the Amazon River. They want to completely describe the organism and your boss is a neuroscience expert. Since you are the only co-op student who has taken a Neurobiology course, you are asked to accompany your boss to Brazil to determine how the nervous system works this new species. In your first set of experiments, you aim to determine the intracellular sodium and potassium concentrations are for these new neurons. You perform all your experiments at 20°C, in normal saline which included 145 mM NaCl and 5mM KCl you find that ENa was +60.6 mV. In Na+ free saline, the resting membrane potential was -58 mV. Assuming that the membrane was impermeable to Cl-, Ca2+ ions are involved and you observe no Na+ current in Na+ free saline.
What are the intracellular concentrations of Na+ and K+? Show your work for partial credit.
Explanation / Answer
We can find the concentrations by using the nernst equation:
Eion = 60/z log10 [Na extracellular] / [Na intracellular]
60.6 = 60/1 log 10 [ 145 / x ]
60.6 = 60 log10 [145/x]
60.6 / 60 = log 145 - log x
1.01 = 2.16 - log x
1.01 - 2.16 = log x
-1.15 = log x
so x = 0.07 M or 70mM
similarly you can calculate for K+
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