October 30, 2007
-
Upload
kirby-galloway -
Category
Documents
-
view
30 -
download
2
description
Transcript of October 30, 2007
October 30, 2007October 30, 2007
Lustyik
Diffussion, thermodiffusion.Diffussion, thermodiffusion.
Biological role of diffusionBiological role of diffusionOsmosis, chemiosmosisOsmosis, chemiosmosis
The microscopic transport of material
Examples for the biological Examples for the biological role of diffusionrole of diffusion
Motion of small molecules:
Diffusion of water in water: D = 2 x 10-9 m2/s
R2
= 6D
R = 1 cm: 8300 s (2 h 18 m)
R = 3 m (E. coli): 7.5 x 10-5 s
Movement of K+ ions through the plasma membrane
Diffusion of K+ ions in water: D = 10-16 m2/s
100 nm x 100 nm
3 x 104 K+ ion /sec
x = 10 nm
C = 500 mM n/t = -D *A/x * c
O2
CO2
Cells and tissues
Blood flow
Diffusion
Diffusion
Légzés
Convective transport
Convective transport
Oxygen and CO2 exchange in the lung
R2
= 6D
CO2
OO22
~1 m
Alveolus of the lung
Kapillary vessel
Alveolar epithelium
Kapillary endothelium
oxigen ~500 s
CO2 ~80 s Doxigen = 10-9 m2/s
DCO2 = 6 x 10-9 m2/s
Diffusion limited rections
A + B AB PkD
k-D
k 1
2kA + B P
Racting molecules Reaction complex
Product
Reaction constants
Ha k-D k 1<<
k 2 kD=
FRAP (Fluorescence Recovery After Photobleaching)
D
Cell
Nucleus
Flu
ores
cen
ce in
ten
sity
Time
FRAP recovery curve
Recovery
Bleaching
Myoblast, expressing a compound that contains GFP (Green Fluorescence Protein)
FRAP
dndt
dd= - Drot
Rotational diffusion, Florescence anisotropy
fR
kTDrot
fR = 8r3
8rkT
Drot= 3
= 2DrotMeasurement with
fluorescence anisotropy
Diffusion potencial
+ +
+++
+++
+
U
Cell membrane
+ +
+++
+++
+
dU =u+ - u-
u+ + u-RTzF
d(lnc)
Diffusion potential:
„ion mobility”
Integration of this equation provides the
Goldman-Hodgkin-Katz equation
October 30, 2007October 30, 2007
Lustyik
Biological role of diffusionBiological role of diffusion
Osmosis, chemiosmosisOsmosis, chemiosmosis
The microscopic transport of material
Solvent
Solute
Semipermeable wall or membrane
Osmosis
AlcoholAlcohol
Este Reggel
Nollet Abbe, 1748
Dutrochet, 1830
Sucrose solution
Water
Models of osmosis:
Vant’Hoff law
Thermodynamic theory
vant’Hoff’s law
= RTc
= p
Solution
h
p = h g
Pure water
Jacobus Hendricus van’t Hoff (1852-1911)
Thermodynamic theory
o1 = o + RT ln xo1
Chemical potential of the solvent:
o1 o2
p1 p2
+ Vpmp1
Vpm: parcial molar volume
o1 = o + RT ln xo1 + Vpmp1
Equilibrium:
o2 = o + RT ln xo2 + Vpmp2
o1 o2
p1 p2
o1 = o2
p2 – p1 = RTVpm
lnxo2xo1
o1 = o + RT ln xo1 + Vpmp1
o2 = o + RT ln xo2 + Vpmp2
o1 = o2
RT
Vpm
lnxo2
xo1
One compartment is pure solvent (xo1=1)The solution is incompressible (Vpm=konstans)
Solvent concentration is low
Vant’Hoff’s law: = RTc
= c (concentration of the solute)
= RTc
Molality: The number of moles of solute in 1 kg of solvent
Molarity: The number of moles of solute in 1 kg of solution
0,3 M glicerin:
0,3 M NaCl (Na+, Cl-):
0,3 Osmol
0,6 Osmol
Ozmolarity =
= molarity x number of dissociated ions
Isotonic solutions:
If their ospmotic pressure is equal
Isotonic solutions with blood and cytoplasm:
0,15 M-os (0,87%) NaCl solution
5,5%-os glucose solution
3,8%-os Na-citrate solution
Isotonic solution
Hypotonic solution
Hypertonic solution
Human and animal cells
Plant cells
Thermoosmosis
Cold Warm
Equal concentrations (at start)
Solvent transport fom the warmer to the cooler side
Dilution concentration
Biological, medical importance and application:
•Lysing red blood cells for clinical laboratory
•Development of oedemas
•Oedema treatment with hypertonic solution
•Mg-szulfát: causing diarrhea
•Hemodialisis of patients suffering from kidney insufficiency
•Dialisis of laboratory specimens
Isotonic solution = isoosmotic solution
• Colloid osmotic pressure
• Membrane is permeable to the solvent
= RTc„reflection” coefficient 0 < < 1
Szemipermeable membrane
„Leaky” membrane
Time
Hid
rost
ati c
pre
ssu
re d
iffe
ren
cep
„leaky”: permeable to the solvent
Volume regulation of living animal cells
Time
Ch
ange
of
cell
vol
um
e
V Shrinking (water uptake)
Volume regulation
Ion transport, release of isotonic solution
Flow maintained by thermodynamic forces:
Jk = Lk1 X1 + Lk2 X2 + … + Lkn Xn
k = 1, 2, 3, …n
Jv = Lpp p + Lpd Jd = Lpd p + Ldd
Onsager equations:
Jv: „volume” flow Jd: diffussion (osmotic) flow
JQ
Je Jm
Jv
T
U
c
p
Heat flow Volume flow
Electric current
Mass transport
Elektric potencial difference
Pressure difference
Concentration difference
Temperature difference
Diffusion
Thermoosmosis
ChemiosmosisChemiosmosis
Q
CyCNADH
I
II
III
NAD+
OH-
OH-
++
O2
Cytochrom system
ADP
ADP ATP
ATP
ATP Synthase
Chemiosmosis
Q
CyCNADH
I
II
III
NAD+
OH-
OH-
++
O2
Citokróm rendszer
ADP
ADP ATP
ATP
ATP Synthase
Ca2+ +Cy A
No “Mitochondrial Permeability Transition Pore”
Membrare potencial in mitochondria
Intact Damaged
Limited and Facilitated Limited and Facilitated DiffusionDiffusion
Additional cellular transport mechanismsAdditional cellular transport mechanisms
Passive transport (simple diffusion)
Facilitated diffusion
Cell membrane
Lipid bilayer
Membrane proteins
www.whfreeman.com
Special, diffusion associated cellular mechanisms
The ability of an organism or cell to move towards or against concentration gradient of a specific chemical compound
Inflamatory response: Migration towards the inflamatory center
Bacterial migration for finding regions that it deems favorable
Sporulation of amebas
Chemotaxis:
Running: flagella turn counterclockwise
„Tumbling”: flagella turn clockwise
Random walking on organelle scale.