L4 Tonicity/Osmotic Pressure

Question 1

is water transport active or passive?

Answer 1

passive - there are no water pumps

Question 2

can water diffuse across lipid bilayers?

Answer 2

yes

Question 3

what gradient will water flow down?

Answer 3

its concentration gradient until it reaches equilibrium

Question 4

what are aquaporins?

Answer 4

water channels exist that allow a greater flux of water across membranes depending on osmotic gradients

increases the permeability of the membrane to water

Question 5

how is water transported?

Answer 5

simple diffusion - has linear kinetics - NO saturation shown

Question 6

the higher the solute concentration… the lower the what?

Answer 6

water concentration

Question 7

What is the formula for osmotic pressure?

Answer 7

= gas constant x temp x molality

Question 8

what is the osmotic pressure gradient?

Answer 8

the difference in osmolality between 2 compartments

Question 9

what are osmotic forces associated with?

Answer 9

concentration of solutes within the fluid with the water wanting to move to an area that has a high solute concentration

Question 10

what is the water flux formula?

Answer 10

= water permeabilityn(aka hydrolic conductivity) x area x reflection coef. x osmotic gradient

only cares about the particles that are stuck

Question 11

what is the reflection coif (sigma)?

Answer 11

forms the basis of tonicity

how willing is a particle to move - if it doesnt’ move, water has to

Question 12

what does iso-osmotic mean?

Answer 12

2 different containers have the same amount of solutes - no solute will flow because equilibrium has been met

Question 13

what does it mean if solution 1 is hypo-osmotic to solution 2?

Answer 13

solution 1 has less solute than solution 2 - if membrane is permeable to solute, it will diffuse until solution 1 is iso-osmotic to solution 2

Question 14

if a solute cannot flow (reflection coef =1), what happens to the water?

Answer 14

water is drawn to high solute concentration since the solute cannot flow - water flows down its chemical gradient = creates hydrostatic pressure

Question 15

when will water flow into the cell?

Answer 15

if osmotic pressure gradient is positive

Question 16

what does a reflection coef of 0 mean?

Answer 16

the substance/solute does not have an effect on water flow - solutes set up their own gradient, don’t need to use water because the solutes flow instead.

Question 17

define tonicity

Answer 17

if a particle can flow between two compartments it will

it a particle cannot flow between two compartments it will cause water to flow to it instead

Question 18

what does it mean by the solution is isotonic to the cell?

Answer 18

if a cell is put in a solution and the cell volume has not changed (no swell or shrink) = non-permeable particle concentrations are equal inside and outside the cell

Question 19

what does a hypertonic solution mean?

Answer 19

solution contains more non-permeable particles than the cell - and water is drawn out of the cell up osmotic gradient - cell will shrink

Question 20

what does a hypotonic solution mean?

Answer 20

solution contains less non-permeable particles than the cell - and water is drawn into the cells up its osmotic gradient - cell will swell

Question 21

all hypo-osmotic solutions are ____

Answer 21

hypotonic