Lecture 3 and 5 Biophysics of the Neuronal Membrane pt 1 and 2 Flashcards
(60 cards)
briefly describe the structure/environment of neuronal membrane
lipid bilayer
transmembrane protein complexes form channels/pores with selective passing of ions
extracellular and intracellular fluid composed of water and ions dissolved
define ions
atoms/molecules that have lost or gained charge (electrons)
what’s a cation?
positive ion
what’s an anion?
negative ion
what unit is used to describe the concentration of solutes (ions) in a solution?
Mole
define a mole
a mole of substance is constituted by 6.022x10^23 of that substance
what is 1 Molar (M) solution?
1 mole of solute dissolved in 1 litre of solution
how will solutes travel in a concentration gradient with permeable membrane?
from an area of high to low concentration until there’s no difference in concentration
as well as concentration gradient, what other factor effects ion flow?
electrical charge
what is electrochemical equilibrium?
when the concentration gradient is opposite and equal to that of its electrical gradient
what does the Nernst equation calculate?
the equilibrium gradient of a given ion
what does the membrane potential (Vm) define?
the difference in potential between inside and outside the cell
write out the Nernst equation
Es = RT/ZF ln([s]out/[s]in)
define the terms of the nernst equation and their associated values
Es= equilibrium potential of ion (volts)
R= universal gas constant = 8.314 J/mol
T= temp = celsius + 273.15= K
Z- charge of ion e.g. +1 or -1
F= faraday’s constant- 96,485 C/mol
what does an Na+/K+ion pump do and why?
actively (using energy) pumps out 3 Na+ and in 2 K+, this overall pushes +1 out of neuron contributing to its negative potential
it maintains resting potential actively
what are the nernst/equilibrium potentials (Es) for K+ and Na+?
Ek ~ -80mV
ENa ~ +58mV
what 2 factors determine whether Na+ or K+ drive the neuronal membrane to their equilibrium potential?
permeability and concentration gradients
if Vm= Ek, what does this mean for the flow of K+?
there will be no net passive current of K+ ions- this would be the equilibrium potential of K+
what happens to the membrane with respect of K+ if Vm>Ek
the membrane has become depolarised
This will cause an efflux of K+ in order to restore Vm to Ek
What happens to the membrane with respect to K+ if Vm<Ek?
the membrane has become hyperpolarised
this will cause influx of K+ to restore Vm to Ek
define reversal potential
the Vm value which changes direction of net current of a particular ion
if Vm is not equal to Es, what 3 factors does the net current depend on?
Vm potential
Concentration gradient of ion
Membrane permeabillity for ion
which 2 ions mostly determine the permeability of resting membrane potential?
Na+ and K+
what are Na+ and K+ ‘trying’ to do do membrane potential?
push it to that of their equilibrium potential (-80mV for K+ an +58mV for Na+)
