Question

In a laboratory, scientists often study neurons in isolation, outside of a living
creature, in a dish. In this setting, one can have a good deal of control over the
local ionic environment in which the cell exists, because we can control the
makeup of the solution – the 'medium' – in the dish. This situation is a bit like
replacing the extracellular fluid that the cell would normally be bathed in with
some other fluid.!

There are a variety of different kinds of media that scientists use for different
purposes. Let’s consider a few standard ones, including Dulbecco’s Modified
Eagle’s Medium (DMEM)* and "depolarization" medium.!

The table below lists the ionic concentrations for these media. The "intracellular"
column lists the concentrations inside a particular neuron. All concentrations
below are in mM (millimolar).!
!
ion/ Intracellular/ DMEM /"depolarization medium"
K+ /140 /5.3/ 55
Na+ /10/ 154 /105
Cl- /12 /119/ 119
Ca2+/ 0.0001 /1.8/ 1.8

Based on this chart, what is the Nernst potential for K+ for the cell, bathed in
DMEM at 37C?!

Check the best option!
• 87 mV!
• -87 mV!
• -25 mV!
• 25 mV!
• -60 mV!

Answer 1

Second Question:

What is the Nernst potential for Cl- in DMEM at 37C?!
Check the best option!
• 80 mV!
• -80 mV!
• 61 mV!
• -61 mV!

Third question:

What is the Nernst potential for Na+ in DMEM at 37C?!
Check the best option!
• 73 mV!
• -73 mV!
• 63 mV!
• -63 mV!

Answer 2

-25
80
63