Lecture #79 & 80
permeable to water but no solute
different from diffusion because it has a semipermeable membrane
what is the cytoplasm osmolarity of a regular cell ?
300 m Osmole
what reflection coefficent is completely permeable?
water only moves in respone to what?
towards an increased osmotic gradient
what is fick's first law equation
rate of solute movement is equal to concentration times reflection coefficent
J=θ* [osmolarity of solute]
simple diffusion characteristics
linear increase / non saturable
use no proteins
no substrate selectivity
facilitate transport features
move hydrophilic solutes
can be active ( use ATP)or facilitated ( w/o ATP)
use a protein
specific inhibitors and substrate selectivity
What are the fastest type of facilitate transporters
channel aka pores
active transporters, and diffusive transporter fit under the category of?
what some example of facilitated diffusive transporters
what are the differences between primary active transport and passive transport
- uphill or against gradient movement
- uses ATP
moves down gradient
how are channels/pores regulated?
by gating ( different factors that affect open and closed state?
pore lined with selective binding sites
how much current can pass through a single pore per unit time
how is open probability caculated ?
percent open/percent closed
what is intracellular ligand gating?
GABA or acetylcholine activated gates
what is extracellular ligand gaintg?
Ca or ATpP channels
what molecules control voltage gated
Na+ k+ Cl0 and Ca2+
how do carrier usually transport
due to a conformational chane
this can have asymetry carrying capacity based on what surface the the binding site is on
how does the NAK ATPase acrive transport carrier work?
3 NA is movin out
2 k is moving in
and 1 ATP is used
why are primary active transporters like Na-K ATPas so useful
They generate a transmemebrane gradient that drive passive transport of other solutes
compared to pores/channel, carrier transport in what speed
>10^6 ions movement /second
characteristic of channels/pores
only move passively ( down gradient)
aquesion soltuion filled pore spans the memebrane
basic properties of channels
what kind of carrier moves na and glucose
symporter moving them in the same direction down their gradietn
what allows human to retain water
different concentration og ions inside versus outside of the cell
electronegative inside vs. outside
this is maintained by immobile negavtive chareges of protain
when calculating the nerst equation you only need to calculate for which ion and why
k because K is the primary ion that cntributes to the resting potential because the otehr ions have very little permeability
what is th nerst equation (simplified)
-61log(concentration inside/conc. outside)=____mV
what are leaks /
when a molecule leaks into the cell via passive diffusion transport
what are pumps
intracellular q levels keep low because active transporter start to move Q out of the cell up/against its gradient
what is net updtake
more solute is moving in that out
intracellular concentraionof ion is increasing while extracellular is decreasing
what is equailibrium
equal transport inside and out of cell
same amoutn in and out
what is subtrate depletion
capillay is always releasing intot he interstitum since interstium is off a much large volume
these compartments never reach equilibrium
alpha intercalated cell function
secrete basic HCo3 secreting
Lecture #79 & 80
membrane transport physiology