The Nernst Equation Flashcards
What is the Nernst Equation used for?
To calculate the equilibrium potential for a particular ion
The equilibrium potential is the voltage at which the net movement of the ion across the membrane is zero.
What is the concentration gradient for Na+ inside and outside a cell?
Outside: 150 mM, Inside: 15 mM
This results in a ratio of 10:1.
What is the equilibrium potential for potassium ions (E_K) at 37°C using the Nernst equation?
E_K = 61.5 log10(K_o/K_i)
Where K_o is the concentration outside and K_i is the concentration inside.
Fill in the blank: The resting membrane potential (RMP) is most permeable to ______.
K+
What is the ratio of K+ concentration outside to inside the cell?
Outside: 5 mM, Inside: 100 mM
This results in a ratio of 1:20.
What happens when the permeability of Na+ increases?
RMP will become more positive.
True or False: At equilibrium potential, there is a net movement of the ion.
False
At equilibrium potential, the electrical and concentration gradients balance each other.
What is the value of z for Na+ in the Nernst equation?
+1
What does the variable ‘V’ represent in the context of the Nernst equation?
Voltage (potential difference in Volts or mV)
What is the formula for work done due to the concentration gradient?
Work = R · T · ln(c_i/c_o)
Where R is the gas constant, T is temperature in Kelvin, c_i is the concentration inside, and c_o is the concentration outside.
What is the effect of a negative resting membrane potential on Na+ ions?
Na+ will enter the cell down both electrical and concentration gradients.
What is the formula for total work in the context of ion movement?
Total work = z · F · V + R · T · ln(c_i/c_o)
Fill in the blank: If the concentration inside equals the concentration outside, then ln(1) = ______.
0
What does a positive work value indicate for ion transport?
Energy is needed to move the ion across the membrane (active transport).
What is the resting membrane potential (RMP) for a typical cell?
-70 to -60 mV
What happens when K+ leaves the cell down its concentration gradient?
It makes the inside of the cell more negatively charged.
What is the equilibrium potential for Cl- given that E_Cl = RMP?
-65 mV
Fill in the blank: The gas constant R is ______.
8.314
What is the significance of the Nernst equation in cellular physiology?
It helps predict the direction of ion movement based on concentration gradients.
What is the formula used to convert Nernst equation results to mV?
V = 61.5 · log10(c_o/c_i) · z
What does the term ‘equilibrium case’ refer to in the context of ion movement?
Work = 0, indicating no energy is required or released.
