Lecture 16 - Solute transport

Question 1

how does facilitated diffusion of charged species work

Answer 1

as diffusion pushes charged molecule to the other side and generates electric force, Electrostatic force pushes other direction to try to even out charge

Question 2

chemical potential

Answer 2

the sum of the concentration, electrical, and hydrostatic potentials (under standard condtions)

Question 3

j (Flux)

Answer 3

amount of solute across the biological membrane per time unit

Question 4

at equilibrium: J(influx) ____ J(efflux)

Answer 4

=

Question 5

______ balances the concentration gradient in ______ of i

Answer 5

Electric field, activity

Question 6

what does passive diffusion of the ion “i” down its concentration gradient result in

Answer 6

a difference of membrane potential across the membrane

Question 7

how is J influx and efflux measured

Answer 7

using the radioisotope of K+ to measure unidirectional fluxes

Question 8

how is the membrane potential measured

Answer 8

microelectrodes

Question 9

what is the typical average potential of plant membranes

Answer 9

-60 to -240 mV

Question 10

how is ako and akc measured

Answer 10

ion-selective microelectrodes

Question 11

how can you calculate the K+ flux system truly at thermodynamic equilibrium

Answer 11

using the Nernst equation

Question 12

Nernst potential

Answer 12

electric field balances the concentration gradient in activity of “i”