Solute Transport Flashcards
Brownian motion
E required for simple diffusion
move down concentrtion gradient
factors in simple diffusion
partition coefficient - how well substance moves into lipid from water (dx)
D- diffusion coefficent - how well moves when in the membrnae (inversely propotional to MW, viscosity of medium)

Fick’s Law
flux (j)
Permeability coefficient x driving force
P = D x A x 1/X
molecules that cross certain area/second = flux
basolateral membrane
faces blood (capillaires)
apical membrane
faces lumen
antiporter
2 ions in opp direction (simple diffusion)
symporter
i.e. glucose and Na+
secondary active transport
co transport
channel
has gate
pore
has no gate (H2O)
Na/K ATPase
primary active transport
requires energy to oppose concentration gradient
[Na] - higher onoutside
[K] -higher on inside
pump Na out and K in
requres ATP
on basolateral membrane of every epithelial cell

paracellular transport
in tight junctions
mediated by claudins

Na+-glucose transport
secondary active transport
Na/K transport pumps Na out wiht ATP (basolateral side)
Na+/glucose (SGLUT) pumps glucose in
Na+ gradient is potential energy
Glucose leaves through GLUT 2 - not dep on gradient/E = through basolateral side

Amino Acids into cell
secondary active transport - also linked to Na+ gradient
Carrier mediated transport
fasterthan diffusion
can saturate
acts as enzyme
diff from ion channels (which have gates)
K+/H+
ATPase - responsible for gastric acid secretion
active
Na+/H+
exchange
responsible for intracellular pH and Na exchange
Cystinuria
for cysteine - transports Cystine in for reabsorption (apical membrane) - transporter
if mutations = urine has 100% of cystine - stones (poorly soluble)
SLCs
drink water or bowel as urater
CDME
analog for cystine
slows crystal growth
Water composition of humans
60% - varies based on muscle mass (less mucscle mass = less water)
muscle –> intracellular space
distribution –> blood volume (BP) and cell volume (cell function)
water - intracell v extracell
2/3 intracellular
1/3 extracellular
water - extracellular distribution
3/4 intracellular (between cells, vessels)
1/4 intravascular (plasma - 75% is in veins) )
plasma composition
93% is water, 7% is proteins and lipids
intracellular osmole
K
solute that keeps water in that compartment
extracellular osmole
Na
intravascular osmole
plasma proteins
effective osmole
i.e. glucose in the absence of insulin
can’t cross any membrane! water always goes in that direction

ineffective osmole
i.e. urea (except in kidney)
always movesacross membrane

permeant solutes
can only lead to transient changes in volume
impermeant solutes
can influence cell volume at steady state
osmolarity
osmoles/L
same as osmolarity in dilute fluids

osmotic coefficient
osmotic coefficient - if not perfectly ionized
i.e. .93 for NaCl
iso-osmotic
same total number of particles
same osmolarity
1 M glucose, 1 M urea, .5 M NaCl
all solutes matter
isotonic
same number of osmotically active particles
same osmotic pressure
.5 NaCl, .333 CaCl2, NOT 1 M urea
non penetrating solutes mater ONLY
NS + D5W
roughly isoosmotic (same number of mosm/kg-water)
NOT isotonic: due to effects of insulin - glucose moves into cells and it is NOT an effective osmole under that coldition (NaCl is effectively extracellular due to Na/K-ATPase)
hypotonic solution
if put cell in it will swell/yse
pressure ECF < presure ICF
isotonic solution
cells stay the same
P of ECF = P of ICF
hypertonic solution
cells will shrink
P of ECF > P of ICF
Cell response in hypertonic ECF
usually cell will shrink and water will leave
cell pumps salts in (NKCC) - Na+, Cl- x2, K+ so not as much water will leave
cell response in hypotonic solution
cell will swell
swelling activates K chanels and K diffuses OUT down electrochem gradient
osmoles leave cell and water follows
paracellular transport
passive but selective variable and regulated
through tight junctions
H2O through paracellular space - in response to osmolarity - Na leaves and H2O neaves
Leaky epihelia
large volume reapsorption - jejumum, proximal tubule
tight epithelia
for concentrtion excreta - collon and collecting duct
ECF volume
determined by total body Na+ content
osmolarity
determined by total body water content
ECF Na+ content
in mmoles
= [Na+] x ECF vol (L)
= osmolality/2 x ECF vol ()
total body osmoles
[osm] X TBW (L)