L1: body fluids & membrane transport - Garcia-Diaz Flashcards
how much BW is H2O
~60%
body weight is water
what is the main component of the human body, accounting for 50-70% of human body weight
water
how much TBW is ICF
2/3
of total body water is extracellular fluid
how much TBW is ECF
1/3
of total body water is intracellular fluid
how much BW is ICF
40%
of body weight is intracellular fluid (2/3 of total body water which is 60% of BW)
how much BW is ECF
20%
of body weight is extracellular fluid (1/3 of total body water which is 60% of BW)
how much of the ECF is interstitial fluid
80%
of the ECF is interstitial fluid
how much of the ECF is PV
20%
of the ECF is plasma volume
T/F BV includes PV and blood cell volume
true
blood volume includes plasma volume and blood cell volume
how do you calculate hematocrit
RBC volume / blood volume
RBC volume / BV =
hematocrit
what is hematocrit
volume percentage of RBCs in total blood volume
typical hematocrit is…
~45%
typical percentage of blood volume occupied by plasma is…
55%
what is transcellular fluid
small part of the ECF contained inside organs (gastrointestinal, cerebral spinal, ocular, etc)… normally ignored in calculations
this is a small part of the ECF contained inside organs (gastrointestinal, cerebral spinal, ocular, etc)… normally ignored in calculations
what is transcellular fluid
the osmolality of most body fluids is
285 mOsm/kg
are the ionic compositions of the plasma and interstitial fluid similar? why?
yes - the capillaries that separate them are highly permeable (although one main difference is the presence of protein in plasma)
are the ionic compositions of the ECF and ICF similar? why?
no – ECF and ICF differ markedly due to their less permeable (less permeable than capillaries) membrane
the main cation in the ECF is…
Na+
the main cation in the ICF is…
K+
the 2 main anions of the ECF are…
Cl- & HCO3-
the main anions in the ICF are…
phosphates and proteins
the intracellular concentration of K+ is
150 mEq/L
the interstitial concentration of K+ is
4 mEq/L
the intracellular vs interstitial concentration of K+ is
4 vs 150 mEq/L
intracellular concentration of Na+ is
12 mEq/L
interstitial concentration of Na+ is
140 mEq/L
intracellular vs interstitial concentration of Na+ is
12 vs 140 mEq/L
how is flux related to moles, area, and time
flux = moles / (area x time) J = M / At
moles / (area x time) =
M / At =
flux
J
how is diffusion coefficient related to molecular weight
D = 1 / sq.rt. MW
concentration gradient =
delta concentration / delta distance
delta concentration / delta distance =
concentration gradient
how is net flux for a neutral solute related to permeability and difference in concentration
net flux = permeability x diff in concentration
J = P dC
what is the principle of macroscopic electroneutrality
charge difference required for electrical potential across membrane is several orders of magnitude smaller than typical ion concentrations – thus no +/- charge differences can be measured chemically across a membrane
why isn’t diffusion efficient over long distances?
t = x^2 / D = x^2 sq.rt. MW
time to diffuse is proportional to the square of the distance diffused – would take forever
chemical driving force of ions across a membrane is
PdC
permeability x delta concentration across membrane
to what factors is permeability related
P = DB/x permeability = diffusion coefficient x partition coefficient / x D ~ 1/sq.rt.MW B = solute solubility in membrane x = thickness of membrane
how are diffusion coefficient, molecular weight, partition coefficient, and thickness of membrane related to solute permeability
D ~ P --> high D = higher P MW ~ 1/P --> high MW = lower P B ~ P --> high partition coefficient = higher P (B = solute solubility in membrane) x ~ 1/P --> greater thickness = lower P
mechanical work =
electrical work =
chemical work =
work = Fd work = qV work = nu (n = moles, u = chemical potential ~ concentration)
RTlnC =
chemical potential (R = gas constant, T = temp, C = concentration)
zFn =
valence x Faraday x moles = charge (q)
1 Faraday = charge in 1 mole of e-
how do you calculate log from ln
lnx = 2.3logx
zFn dV =
q dV = electrical work
@ physiologic temp, electrochemical potential / F =
61 log (Cin/Cout) + zV (z = valence...# +/- charges on ion)
@ room temp, electrochemical potential / F =
58 log (Cin/Cout) + zV (z = valence...# +/- charges on ion)
physiologic temperature
37 degrees C
310 degrees Kelvin
room temperature
~ 20-25 degrees C
electrochemical potential / F =
u/F = k log(Ci/Co) + zV (k = constant)
k log (Ci/Co) + zV =
u/F = electrochemical potential
what are the units of electrochemical potential?
mV
do + charges move from high to low or low to high potential?
high to low
do - charges move from high to low or low to high potential?
low to high
log 0
undefined
log 1
0
log .1
-1
log .5
-.3
log 2
.3
-log x =
log 1/x
log xy =
log x + log y
log x/y =
log x - log y
log x^y =
y log x
nernst equation
Veq = 61/z log(Cout/Cin)
what value does the nernst equation calculate
equilibrium potential (Veq or E) = the electrical potential for a given in/out ion concentration for which the net flux will be zero
equilibrium membrane potential =
61/z log(Cout/Cin)
net driving force of an ion across a membrane =
Vm - Ei
Vm - Veq
membrane potential - equilibrium potential
flow =
conductance x force
conductance x force =
flow
how is conductance related to resistance
g = 1/R conductance = 1/resistance
how is conductance related to permiability
g ~ P
conductance ~ permeability
how is the electric current carried by a permeable ion across a membrane related to the conductance and the ion net driving force?
linearly
I = g (Vm - E)
I = g (Vm -Ve)
T/F for more than one permeable ion at equilibrium across a barrier, Vm = Ve = E1 = E2 = E3… etc
true - the potential is the same for all ions at equilibrium
what is the name for the equilibrium distribution of permeant ions in the presence of non-permeant ions
Gibbs-Donnan equilibrium
at Gibbs-Donnan equilibrium, what is true of
- permeant anion/cation concentrations on the same side of the membrane
- permeant anion/cation concentrations on opposite sides of the membrane
- osmolality on opposite sides of the membrane
- permeant [cations] = [anions] on the same side
- permeant [cations] is > and permeant [anions] is on side with non-permeant protein
is permeant [cations] in the interstitial fluid > or < in the plasma?
permeant [caitons] IF < permeant [cations] plasma
because -proteins in plasma are impermeable
is permeant [anions] in the interstitial fluid > or < in the plasma?
permeant [anions] IF > permeant [anions] plasma
because -proteins in plasma are impermeable
are total equivalents in interstitial fluid > or < in the plasma?
total equivalents IF < total equivalents plasma
(at gibbs donnan equilibrium, due to impermeable -proteins in cytoplasm)
are the concentration differences in plasma and IF due to capillary endothelium impermeability to -proteins small or large? what is the difference in electrical potential?
small. V ~ 1mV
T/F there is a Gibbs-Donnan equilibrium across the membrane of living cells
false - the leak of ions like Na+ and K+ is offset by active transport by Na K ATPase such that they are not able to reach equilibrium
what are the consequences of inhibiting the Na K ATPase pump?
ion concentrations will evolve toward equilibrium, which will increase cytosolic osmolarity, which will draw water into cell and lead to swelling and potentially cell death
at Gibbs-Donnan equilibrium, what is true of the product of ion concentrations on either side of the membrane?
the equilibrium potentials of any two permeant ionic species are equal, regardless of the presence of other ionic species, i.e. ENa+ = ECl- = EK+ = …
so if ENa+ = ECl-
then (k/z) log ([Na]out / [Na]in =
(k/z) log [Cl]out / [Cl]in
zNa = 1, zCl = -1, so
[Na]out / [Na]in = [CL]in / [Cl]out
and [Na+]out x [Cl]out = [Na+]in x [CL]in
in plasma, what are the main anions and their relative concentrations
Cl- > HCO3- > proteins-
in interstitial fluid, what are the main anions and their relative concentrations
Cl- > HCO3-
in ICF, what are the main anions and their relative concentrations
phosphates- > proteins- > Cl- > HCO3-
in plasma, what are the main cations and their relative concentrations
Na+»_space; K+
in interstitial fluid, what are the main cations and their relative concentrations
Na+»_space; K+
in ICF, what are the main cations and their relative concentrations
K+ > Mg++ > Na+
A membrane permeable to small ions but not to proteins separates two solutions, A and B, which contain Na+, K+ , proteins and other ions. In the steady state the concentration of Na+ is higher in A than in B whereas the concentration of K+ is lower in A than in B. Which of the following statements is correct?
A. Na+ cannot be at equilibrium distribution. B. K+ cannot be at equilibrium distribution. C. It is impossible for other ions to be at equilibrium distribution. D. It is impossible for both Na+ and K+ to be at equilibrium distribution. E. None of the above statements is correct.
D. It is impossible for both Na+ and K+ to be at equilibrium distribution.
Two ions of the same charge cannot be at equilibrium Distrubution (i.e. CHEMICAL Equilibrium) with an opposite concentration distribution across the membrane… kind of a nitpicky dirty question…