Question

Consider a cell in which Cl- distributes passively across the membrane according to the membrane potential. The resting membrane potential in this cell is measured to be -60 mV. If the extracellular Cl- concentration is 100 mM, then the intracellular Cl- concentration is:

Answer 1

The exact intracellular Cl- concentration cannot be determined without applying the Nernst equation or having additional cell-specific information.

Step-by-step explanation:

The intracellular Cl- concentration in a cell at resting membrane potential can be estimated using the Nernst equation which relates the ion concentration gradient to the electrical charge across a membrane. Given a resting membrane potential of -60 mV (while typical cells have a resting potential of about -70 mV) and an extracellular Cl- concentration of 100 mM, we can predict the intracellular concentration if Cl- is in equilibrium at that membrane potential. However, without the Nernst equation or additional information on cell specific permeability or other ion concentrations for that particular cell, the exact intracellular concentration of Cl- cannot be determined solely based on the provided data.

Answer 2

1000 mM

Step-by-step explanation:

Using V = -60 mV㏒₁₀[K/K'] where V = membrane potential = -60 mV, K = intracellular concentration = unknown and K' = extracellular concentration = 100 mM

So, V = -60 mV㏒₁₀[K/K']

-60 mV = -60 mV㏒₁₀[K/K']

dividing both sides by -60mV, we have

-60 mV/-60 mV = ㏒₁₀[K/K']

㏒₁₀[K/K'] = 1

taking antilogarithm of both sides, we have

[K/K'] = 10¹

multiplying both sides by K', we have

K = 10K'

K = 10 × 100 mM

K = 1000 mM

So, the intracellular Cl- concentration is 1000 mM