Lecture 11 - AQP1

Question 1

Pf

Answer 1

osmotic water permeability

Question 2

Osmotic water permeability

Answer 2

the permeability to water when an osmotic gradient is applied

Question 3

What happens to water when the cell is in a hypertonic solution?

Answer 3

water leaves the cell

Question 4

What happens to water when the cell is in a hypotonic cell?

Answer 4

Water moves into the cell

Question 5

Pd

Answer 5

Diffusional water permeability

Question 6

Diffusional water permeability

Answer 6

Permeability to water when there is no osmotic gradient

Question 7

What happens to water when the cell is in an isotonic solutioN?

Answer 7

equal water enters and leaves cell/

Influx = efflux therefore no net movement without volume change

Question 8

Pf/Pd>1 means

Answer 8

there is a water pore present int he cell membrane

Question 9

Cartesian diver balance use for…

Answer 9

Used to measure Pd

Question 10

Cartesian diver balance set up

Answer 10

small glass funnel containing cells with an air bubble at the top. The density of air in the bubble determines what level it goes to in the solution

Question 11

Adding pressure to the Cartesian diver balance

Answer 11

increased pressure means the air bubble gets smaller so the diver sinks

Question 12

adding suction to the Cartesian diver balance

Answer 12

air bubble expands so the diver rises

Question 13

Cartesian diver balance experiment

Answer 13

cells equilibrated in water then placed into heavy water solution, D2O exchanges with H2O in cells so the cell becomes heavier so the diver sinks. Apply suction to keep diver at a constant height. measure the pressure needed to keep diver at constant height over time

Question 14

Cartesian diver balance change in equilibrium pressure correlated to change in weight

Answer 14

from this correlation the change inc ell weight can be measured, then it is known how much D2O has moved into the cell so Pd can be calculated

Question 15

Measuring Pf

Answer 15

measure change in cell volume over time when exposed to a hypertonic/hypotonic solution

Question 16

Pf equation

Answer 16

change in volume = Pf x SA x t x change in C

Question 17

red blood cells and water permeability

Answer 17

highest permeability of any cells with a 2.5 ratio

Question 18

AQP1 32kd band

Answer 18

glycosylated version of the 28kd protein

Question 19

AQP1 structure

Answer 19

6TMDs

Question 20

Is CHIP28 a water channel?

Answer 20

circumstantial evidence only, transcript corresponds to the RNA fraction from kidneys that produces greater water channel activity
both CHIP28 and water channel are resistant to enzymatic digestion

Question 21

Experimental CHIP28 evidence

Answer 21

expressed in xenopus oocytes and exposed to hypotonic shock

volume change is rapid and oocytes explode within a few minutes