lecture 3 Flashcards
cell membrane
movement between extracellular fluid and cytosol across the lipid bilayer of particles
intergral (transmembrane) proteins : transport things through cell membrane
main functions of cell membrane
- physical isolation
- regulation of exchange with the environment
- communication between the cell and its environment
leak channels
selective eg. K+channels, Na+ channels, Cl- channel
sodium potassium pump
- form of active transport; goes against concentration gradient (requires ATP)
- pumps 3 Na+ out of the cell
- pumps 2 K+ into the cell
membrane potential
all cells have it
- it is the electrical potential across the membrane
- generated by the selective permeability of the membrane to particular ions
- usually 70mV
- depends on concentration gradients of K+ and Na+ and,
- relative permeability of K+ and Na+
resting membrane potential
more potassium leak channels than sodium channels = Potassium is more permeable
at rest , Pk > Pna (permeability)
equilibrium potential
the electrical potential (mV inside the cell) required to exactly offset the force of the concentration gradient of the ion
Use nerst equation to describe the equilibrium potential for an ion
nerst equation
used to describe the equilibrium potential for an ion (concentration and electrical gradient)
Eion = 61/Z log (Cout/Cin)
Eion : equilibrium potential of ion in mV
Z : valence of ion
C out : extracellular concentration
C out : intracellular concentration
Goldman-Hodkin Katz equation
membrane is permeable to many ions and the permeability varies depending on the ion
each ion will affect the resting membrane potential depending on its concentration gradient and permeability
Vm = 61 log Pk [K out] + P na [Na out] + Pcl [Cl in]/ Pk [Kin] + Pna [Nain] + Pcl [Clout] = -70mV
summary of resting membrane potential
generated largely because of the movement of K+ out of the cell
