Origin and maintainence of resting membrane potential Flashcards
What is the structure of the cell plasma membrane?
Phospholipid bilayer
What 2 types of substances is the cell plasma membrane largely impermeable to?
Phospholipid bilayer is largely impermeable to hydrophilic compounds and ions
Is the plasma membrane of a cell fully permeable to substances other than hydrophilic compounds and ions?
No, the plasma membrane is selectively permeable due to enzymes, ion channels, signal receptors in the membrane
Does the plasma membrane have equal permeability for potassium and sodium ions?
No, the plasma membrane is much more permeable to potassium ions than sodium ions
What is the permeability ratio of sodium ions compared to potassium ions, and what does this indicate?
0.013
Indicates that plasma membrane is largely impermeable to sodium ions, but largely permeable to potassium ions
In the origin of the resting membrane potential, why do potassium ions first enter the cell, and how does this affect the inner cell charge?
Inner cell is negatively charged due to protein anions, which attracts positively charged potassium ions so that the inner cell will have neutral charge?
In the origin of the resting membrane potential, how is the diffusion force primarily generated?
After potassium ions have entered the cell, there is now a higher concentration of potassium ions inside than outside cell, generating a diffusion force to cause the potassium ions to diffuse down the concentration gradient
In the origin of the resting membrane potential, how is the electrical force primarily generated?
Potassium ions diffusion out of cell down concentration gradient causes inner cell to become more negatively charged than outside cell, the difference in charges generates the electrical force
How do diffusion and electrical forces interact to eventually generate the resting membrane potential?
Diffusion and electrical forces balance out
How does permeability of different ions influence the value of the resting membrane potential?
Ions that cell membrane are largely permeable to have more influence on resting membrane potential than ions that cell membrane has low impermeability to
Is the resting membrane potential close to equilibrium potentials of ions that the membrane is largely or slightly permeable to?
Resting potential is closest to equilibrium potentials of largely permeable ions but is slightly influenced by equilibrium potentials of slightly permeable ions
Why is the resting membrane potential slightly more positive than the equilibrium potential of potassium ions?
The resting membrane potential is slightly influenced by equilibrium potential of sodium ions, which the cell membrane is largely impermeable to so this will make increase the resting membrane potential
What is the equilibrium potential of an ion?
Value of the diffusion potential/electrical potential difference across cell membrane of an ion that exactly balances/opposes concentration gradient, as there is an symmetrical distribution of ions
When is electrochemical equilibrium of an ion reached?
Diffusion and electrical forces acting on that ion are equal magnitudes and opposite
What are the 2 definition of what is calculated by the Nernst equation?
the equilibrium/diffusion/nernst potential that promotes equal diffusion of potassium in both directions despite the different concentrations
the concentration ratio of an ion necessary to generate a particular potential difference
What is the Nernst equation, and what do the symbols stand for?
Ex: Equilibrium potential of the ion
R: Universal gas constant
T: absolute temperature
Z: valence/charge of the ion
F: Faraday constant
Xout: extracellular concentration of the ion
Xin: intracellular concentration of the ion
What is the Goldman equation used to calculate?
calculates equilibrium potential of a cell based on effects of all charged species and their membrane permeability (P)
What does the Hodgkin equation calculate?
Calculates equilibrium potential of cell based on potassium and sodium ion permeability and concentrations only
