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23 Cards in this Set

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Water transport as described through the kidney

glomerular filtrate: where is it reabsorbed in the kidney?

how do membranes acheive selectivity through permeability?
in the proximal tubule and
in the descending thin limb epithelial cells
through aquaporin-1 (AQP1)

permiability selectivity: aquaporins
how does the Hormone vasopressin increase membrane water permeability ?
stimulates redistrubution of AQP2 from cytoplacmic vesicles to apical membrane of PRINCIPLE cells
AQP-1
monomer
congegrates as tetramer? but water slides down each monomer
6 mem spanning helices
loops B and E loop into membrane and form the pore
NPA motifs
water can move in both directions
water is just the right size to fir, an arg and a his keep H+ from going through, only water
selectivity without loosing rapid exchange
osmosis
net flow of water across a membrane
osmotic pressure
definition
what provides osmotic pressure in a cell?
driving force for osmosis
the pressure needed to prevent movement of water from a place of low solute to a place of high solute
in a cell the SOLUTES provide osmotic pressure
what does osmotic pressure depend on?
the osmolarity of solutes
the permeability of membrane to solutes
osmolarity
Osmolarity measures the gradient for water assuming all the osmotic solute is impermeant. It is simply a count of the number of dissolved particles. Therefore a 300 millimolar solution of glucose, a 300 millimolar solution of urea, and a 150 millimolar solution of NaCl each have the same osmolarity.

colligative property
colligative property
depends on total number not the nature/size/charge
osmolarity
eqn
g(# of particles/mole)
/ C ([]mmol/L)

more solutes = more osmolarity
hyperosmotic
hypo-osmotic
iso-osmotic
hyper - higher osmolarity
hypo- lower osmolarity

iso - 300 mOSM is standard intracellular osmolarity
reflection coefficient
of 0
of 1
ex for each
describe ease of solute passage through membrane
0 - freely permeable, solute exerts no osmotic pressure/no driving force
urea is close to zero
1 - impermeable, provides osmotic pressure across the membrane
ie serum albumin/ions/proteins etc
vant hoff eqn
described osmotic pressure of a solution
SEE pg 211
tonicity
biological property
dependant on concentration of impermeable solute
Tonicity is a functional term that describes the tendency of a solution to resist expansion of the intracellular volume.


osmolarity * reflection coeff
hypoTONIC solution causes cell to swell
hyperTONIC solution causes cell to shrink
what happens if you add more NaCl to an iso-tonic solution into ECF(extra cellular fluid)?
cell swells . . .
SEE PAGE 213!
AQP disease
hf
AQP2 protein may be involved in most water imbalances
Diabetes insipidus results in vasopressin which causes channels to be open all the time?
Van't Hoff
1 osmolarity - [] of osmotically active particles. only dependent on total # of particles
gC (particles per molecule/

2 reflection coefficient
mM vs mOsm, calc osmolatiry
100mM urea 100mOsm
100mM NaCl 200mOsm
200mM CaCl2 600mOsm
isoosmotic
two solutions have the same osmolarity
hyper osmotic
higher than 300 mOsm
hypo osmotic
lower than 300 mOsm
reflection coeff
ease through which [articles pass through the plasma mem

no go = 1 proteins
good to go = .2 urea
NOTE
CELL IS ALWAYS PLACED IN AN
INFINITELY LARGE BATH. volume of cell cant change the volume of the surrounding solution
150mM NaCl
100mM NaCl
300mM urea
means 300mOsm means isotonic
means 200mOsm means hypoosmotic, hypotonic(water is going in)

300mOsm - isoosmotic, hypotonic! urea will go into cell by diffusion to achieve [] balance, where solutes go, water will follow, thus the cell swells