A researcher examines the voltage across the inside of a neuron from a fish previously unknown to science. She places one electrode inside the cell and has a second electrode in the extracellular solution. She sets the extracellular potassium concentration equal to 1 mM. She measures a transmembrane potential of - 60 mV at room temperature. What is the likely concentration of potassium on the inside of this cell?

The best answer to the question: What is likely the concentration of potassium on the inside of this cell, would be: 10 mM.

Explanation:

It must be remembered that plasma membranes of cells, especially neuron plasma membranes, are highly susceptible to ion changes and ion gradients on their intercellular and extracellular matrix. Potassium, and whenever present calcium, are particularly important in a membrane's capacity to generate action potentials, and be depolarized, because their movement inside and outside of the cell with generate an electron gradient that will literally charge the cell, until it becomes so much, that it is ready to fire.

Usually, potassium appears in greater concentrations inside cells and at much lesser concentrations outside of it. If these values (in the case of the fish 1 mM outside of the neuron and 10 mM inside) are changed, say as the sodium-potassium pumps are activated by stimulation of the neuron, then the cell's plasma membrane's polarity will change until it becomes ready to depolarize, or as we commonly call it, fire. In the case of this fish, the result of measures show that the voltage of the membrane in the neuron is stable at - 60mV because the balance between the intra and extracellular potassium in regards to concentration gradients, is stable and unchanging.