Membrane Potential Flashcards
What is the role of the plasma membrane?
make separation between the extracellular and intracellular milieu
What is the role of the proteins within the phospholipid bilayer?
- help cells communicate with neighboring cells
- adapt to its environment
- sense environment
What is the essence communication within the plasma membrane?
transmembrane protein function and regulation
What are the ways transport across the membrane can take place?
diffusion, carrier proteins, and ion channels
What is the purpose of carrier proteins?
to help solutes that are too big or not charged cross the plasma membrane
How do ion channels help solutes cross the plasma membrane?
forms canal/water soluble channel that provides adequate environment for ions
What type of molecules can cross the membrane readily?
small and lipophilic molecules
What are aquaporins?
ion channels that are proteins in the plasma membrane that allow H2O to flow
What is the voltage difference across the plasma membrane?
inside the cell: more negative
outside the cell: more positive
How is membrane potential created?
by voltage difference produced by charge gradient
What is the formula of membrane potential?
change in E= Em = Ein - Eout
Is the typical resting membrane potential positive or negative?
negative
What is the flow of a membrane potential?
rest -> depolarization -> repolarization -> rest
Action potential is equal to …
change in membrane potential
Is the movement of uncharged molecules affected by membrane potential?
NO
What is electrochemical potential?
free energy acting on charged particles
What is the formula for electrochemical potential?
RT * ln (conc in. / conc. out) + zFE
What is the nernst equation?
Eeq= 58z * log (conc out / conc. in); predits equilibrium potential
What does the direction of ion movement depend on?
equilibrium potential and membrane potential
At what point will the cation move into the cell?
when the membrane potential is more NEGATIVE
What determines the resting membrane potential?
the permeabilities and conc. of Na+, K+, and Cl-
Why is the membrane potential closest to the equilibrium potential of K+?
because of more K+ channels being open
What is the Goldman equation?
Er = 58 * log ( Pk[Kout] + PNa [Naout] + PCl [Clin] / Pk[Kin] + PNa [Nain] + PCl [Clout]
What is able to change the membrane potential?
- change permeability of one of the ions
- open or close the channels of certain ions
- change conc. gradient across the membrane
When external K+ conc. is INCREASED, how does the membrane potential react?
gets less NEGATIVE; cell becomes depolarized
What are the major classes of ion channels?
- leak (constitutively)
- stretch-activated
- ligand-gated
- voltage-gated
What are leak activated channels?
- active channels that provide a permeation path for a specific ion
- maintains resting membrane potential of the cell
What class of ion channels is responsible for maintaining the ionic composition of the intra and extracellular environments?
leak activated channels
What are stretch activated channels?
- proteins change conformation when the plasma membrane is stretched
- aqueous pore is formed
What occurs in a ligand gated channel?
neurotransmitter binds -> channel opens= flow of ions
A voltage gated channel is …. at rest
closed
What is a voltage gated channel?
when membrane potential is depolarized, ion channels sense voltage change and open
