membrane potential Flashcards
the plasma membrane has — that encloses cell and its embedded with — that acts as —-
the head is —-
tails are —
- phospholipid bilayer
-protein - receptor/channels
- hydrophilic ( choline phosphate and glycerol )
- hydrophobic ( fatty acids )
plasma membrane:
1- all cells are surrounded by —
2- functions:
3- membrane protein includes:
- All cells surrounded by fluid lipid-protein bi-layer
- fucntions:
1-Forms basic structural barrier enclosing cell
2-Serves as barrier to free passage of substances
3-Cell can maintain different mixtures of substances inside and outside (nutrients, waste products)
4-Fluidity of membrane/cell
5-Communication between cells
6-Response to external stimuli - membrane proteins include:
1- intergral/ transmembrane
2- extrinsic / peripheral
movement across the plasma membrane
1- Lipid soluble & small uncharged molecules as — are:
— diffusible
- movement is driven by —-
2- charged ( ion) / water soluble:
have — interior of PM which prevents —–
3- the plasma membrane is said to be —-
- freely
- 02
- concentration gradient
- hydrophobic interior
- free movement
- selectively permeable
transport across the membrane can be by:
1- diffusion ( (e.g., O2, CO2, lipid (fat)-soluble )
2- Protein-mediated membrane transport by channel or carrier proteins
3- endocytosis ( phagocytoses , pinocytosis )
4- excosytosis
separation of opposite charges gives rise to — as opposite charges attract
( diference in cations and actions across PM)
- this can make:
1- — difference across the membrane
2- excitable cells actively induce —-
3- basis for electrical excitability of —–
4- harnessed for —-
- how is this membrane potential done:
- the plasma membrane allows cells to establish difference in —- of key – ions across the pm
- magnitude of potential depends on degree of —-
- membrane potential ( all cells have membrane potential )
1- electrical
2- induces change
3- nerve and muscle
4- transporting substance - concentration
- charged ions
- degree of charge separation
1-absence of membrane potential leads to —- despite the membrane barrier no charge — across the membrane so no —-
2- presence of membrane potential will have the remained of extra and intracellular fluids —- and —- are responsible for potential
- electrical neutral
- difference
- no membrane potential ( between extra and intracellular)
- electrically neutral
- separated charges
- ca is more concentrated —
- k is more concentrated —
- outside
-inside
1-resting membrane potential (RMP):
- Cell membrane is more —- inside than outside
-neuron is about —
2- this is responsible for:
1- —- of k+ , na+ , A- ( large protein anions ) between inside and outside of the cell
2- —– of PM to k+
- negative
- -70mV
- unequal distribution
- selective leakiness
( check slide 20)
—– establishes K+ & Na+ concentrations across PM , its a — enzyme which transports — out and — in
- uses —- and it takes
- establishes concentration gardietns for —
- Na+/k+ ATPase pump
- membrane spanning enzyme
- 3 na+
- 2 k+
- uses energy ATP (and it takes 200 million ions/sec
- na+ and k+
( check slide 22 for graph )
RMP concentration:
1- Unequal transport of positive ions by Na+/K+-ATPase also generates —-
2- inside becomes a little – with regards outside bc of –
what is repsonsible for most potential ?
- diffusion of k out of the cell — concentration gradient established by — leaves the inside more —
- small potential
- negatively
- 3na + and 2k+ in
- down
- pump
- negative
despite the PM barrier , PM contains many k+ —- which allows the — of k+ at — out of cell – its concentration gradient
- leaking channels
- diffusion
- at rest
- down
-K+ leaks out because of — concentration gradient, making inside —-
- —- ) are left behind
further increases inside negativity
- resting membrane potential is —
- large
- -ve
- A- cant pass
- -70mV
1—- acts as a driving force for diffusion of K+ out of the cell
2-The residual negative charge acts as a —– drawing K+ back into the cell
3- —-electrical force balances chemical force, no net transport
chemical gradient
electrical driving force
equilibrium
nernest equation is :
E = + 61 x log Co/Ci
E = equilibrium potential for ions in mV
61= constant incorporating Gas constant R;
absolute temperature (T), ions valence when the valence is +1: as we have Na+/K+(z), the Faraday constant and logarithmic conversion (natural to base 10) 61 = (RT/zF
Co = concentration ion outside
Ci = cocnetration ion inside
—- is concentrated outside cell
—– would “drive” Na+ into cell
plasma merman his very – permable to Na+ bc of —
- na+
- Concentration and electrical gradient
- little
- very few leak channels for sodium
