lecture 18: osmolarity and tonicity

Question 1

diffusion

Answer 1

process through which atoms or molecules intermingle because of their random thermal motion

Question 2

net diffusion

Answer 2

directional movement due to a greater concentration in one location compared to another
continuous until concentration gradient is eliminated
—-stuff will be moving but its not directional

Question 3

factors that affect net diffusion

Answer 3

1. area of plane of contact (surface area)
   —greater area = larger pathway = greater rate of diffusion
2. concentration gradient
   —–larger = increase rate of diffusion
   —–net diffusion as 0 if both containers have same concentration
3. size of molecule
   —-smaller = move faster
4. viscosity of a medium
   —-lower = faster diffusion
   —-ex: matrix between alveoli and blood capillary is not very viscous, pulmonary fibrosis makes matrix viscous and harder for O2 to move from lungs to blood
5. distance
   —-shorter = faster diffusion
   —–increases exponentially

Question 4

osmolarity

Answer 4

number of particles in a solution (osmol/L)
different than composition of solution
not what its made out of but amt. of particles
water moves from solution of low solute to one of high solute
nonelectrolytes do not dissociate when places in solution
electrolytes do dissociate in solution
osmolarity of most fluids in human body = 300 mOsM

molarity x dissociation # = osmolarity

Question 5

isosmotic

Answer 5

two solutions have equal number of solute particles per unit volume
generate the same osmotic pressure

Question 6

hyperosmotic

Answer 6

one solution generates higher osmotic pressure

Question 7

hyposmotic

Answer 7

one solution generates lower osmotic pressure

Question 8

permeable membrane

Answer 8

solute and solvent cross
volume is the same too between both compartments

Question 9

semipermeable membrane

Answer 9

only the SOLVENT crosses
ex: water goes from B to A
go to where more solute is
solute generates higher osmotic P —> osmosis
increase in volume for A

Question 10

osmosis

Answer 10

net movement of water molecules from the area of lower concentration of solutes to the area of higher concentration of solutes

Question 11

selectively permeable membrane

Answer 11

solvent can cross
solutes have different permeabilities
only looking as osmolarity does not determine what moves

Question 12

permeability coefficient

Answer 12

indicates how fast something crosses
measured in cm/s

Question 13

tonicity

Answer 13

water crosses due to the movement of solutes
solutes are osmotically active or inactive
used to describe the solution relative to the cell

Question 14

isotonic

Answer 14

no net movement of H2O
no change in cell volume
water will still be moving through membrane but no loss/gain to the areas

Question 15

hypotonic

Answer 15

ex: A is hypotonic to B
A lost water
water moves to B

if cell is hypertonic compared to solution —> cell gains water —-> cell swells and may burst —-> lysis

Question 16

hypertonic

Answer 16

ex: B is hypertonic to A
B gained water
water moves to B

if cell is hypotonic compared to solution —-> cell loses water —> cell shrinks —> crenation where no fluid is inside