Solute transport

Question 1

ion diffusion is driven b y

Answer 1

chemical potential difference x membrane permeability

Question 2

chemical potential difference is driven by differences in –

Answer 2

concentration, pressure, and electric potential (voltage)

Question 3

– are large driving forces

Answer 3

concentration and voltage differences

Question 4

at equilibrium, there may remain a – as well as a small concentration gradient across the membrane

Answer 4

membrane potential (voltage difference)

Question 5

a substantial voltage difference may be generated even though the number of unbalanced ions is –

Answer 5

negligible

Question 6

a membrane potential of – may be generated by a concentration difference across the membrane of 0.001%

Answer 6

-100 mV

Question 7

all living cells exhibit a membrane potential due to the – between the inside and outside of the cell

Answer 7

asymmetric ion distribution

Question 8

membrane potential can be determined by – the cell and external solution with microelectrodes

Answer 8

probing

Question 9

Nerst equation gives the – expected across a membrane at equilibrium if the voltage across the membrane is known

Answer 9

concentration gradient

Question 10

Goldman equation predicts the diffusion potential from Na+, K+, Cl_ the ions with the – cellular concentrations

Answer 10

highest

Question 11

for most ions, experimentally determined ion concentrations differ from Goldman equation prediction indicating –

Answer 11

active transport

Question 12

cytosol and – differ strongly in ion uptake

Answer 12

vacuole

Question 13

– is taken up passively by both cytosol and vacuole unless concentration is very low, then it is taken up actively

Answer 13

K+

Question 14

Na+ and Ca2+ and excess protons are – out of the cytosol into the vacuole and extracellular spaces

Answer 14

actively pumped out

Question 15

anions are – into the cytosol

Answer 15

actively taken up

Question 16

effects of ATP can be provided by using – to poison mitochondria, which depletes ATP

Answer 16

CN-

Question 17

when CN- is added to cell, the membrane potential falls to that – by the Goldman equation (also cytosol becomes acidic because H+ remains in cell)

Answer 17

predicted

Question 18

facilitate the passage of selected ions and other polar molecules

Answer 18

transport proteins (transporters)

Question 19

in arabidopsis, about – of all genes code for transporters

Answer 19

5%

Question 20

can be specialized to only allow one direction ion movement

Answer 20

channels

Question 21

carrier mediated transport is –

Answer 21

passive or active

Question 22

secondary active transport can be –

Answer 22

symport or antiport

Question 23

vacuole has a low pH relative to the cytoplasm

Answer 23

hyperacidic

Question 24

rate of ion uptake =

Answer 24

rate of protein activity

Question 25

Michaelis-Menten kinetics: rate of ion uptake plotted against –

Answer 25

ion concentratio

Question 26

A saturation (Michaelis-Menten) curve appears

Answer 26

rate increase and then stabilizes

Question 27

max rate of uptake

Answer 27

Vmax

Question 28

ion concentration to drive 50% to Vmax

Answer 28

Km

Question 29

low Km

Answer 29

high affinity

Question 30

ions are mostly absorbed through –

Answer 30

root hairs

Question 31

at endodermis, the ions but enter the – because of the suberized Casparian strip

Answer 31

symplast

Question 32

casparian strip control ion entering xylem and prevents – out of xylem to the soil via apoplast

Answer 32

diffusion of ions