460 likes | 562 Views
Diffussion, thermodiffusion. Biological role of diffusion Osmosis, chemiosmosis. The microscopic transport of material. October 30, 2007. Lustyik. Examples for the biological role of diffusion. 2. = 6D t. D. R. R = 1 cm:. 8300 s (2 h 18 m). R = 3 m m (E. coli):. 7.5 x 10 -5 s.
E N D
Diffussion, thermodiffusion. Biological role of diffusion Osmosis, chemiosmosis The microscopic transport of material October 30, 2007 Lustyik
2 = 6Dt D R R = 1 cm: 8300 s (2 h 18 m) R = 3 mm (E. coli): 7.5 x 10-5 s Motion of small molecules: Diffusion of water in water: D = 2 x 10-9 m2/s
Dx = 10 nm DC = 500 mM Dn/Dt = -D *A/Dx * Dc 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
Convective transport Diffusion Convective transport O2 CO2 Diffusion Légzés Blood flow Cells and tissues
2 D R = 6Dt Oxygen and CO2 exchange in the lung CO2 Alveolus of the lung ~1 mm Alveolar epithelium O2 Kapillary vessel Kapillary endothelium toxigen ~500 ms Doxigen = 10-9 m2/s tCO2 ~80 ms DCO2 = 6 x 10-9 m2/s
P A + B k k Ha k k << D D k k k -D -D 2 1 1 k = 2 Diffusion limited rections Reaction constants P A + B AB Racting molecules Product Reaction complex
FRAP (Fluorescence Recovery After Photobleaching) Cell D Nucleus
Bleaching FRAP recovery curve Fluorescence intensity Recovery Time
FRAP Myoblast, expressing a compound that contains GFP (Green Fluorescence Protein)
dn dr dt df = - Drot f Rotational diffusion, Florescence anisotropy
kT Drot= fR fR = 8phr3 Measurement with fluorescence anisotropy kT Drot= = 2Drott Df 2 3 8phr
Cell membrane + + + + + + + + + + + + + + + + + + DU Diffusion potencial
RT u+ - u- d(lnc) dU = zF u+ + u- Diffusion potential: „ion mobility” Integration of this equation provides the Goldman-Hodgkin-Katz equation
Biological role of diffusion Osmosis, chemiosmosis The microscopic transport of material October 30, 2007 Lustyik
Osmosis Semipermeable wall or membrane Solvent Solute
Alcohol Alcohol Nollet Abbe, 1748 Water Este Reggel Dutrochet, 1830 Sucrose solution
Models of osmosis: Vant’Hoff law Thermodynamic theory
p = RTc h p = h r g vant’Hoff’s law Pure water p = p Solution Jacobus Hendricus van’t Hoff (1852-1911)
+ Vpmp1 p1 p2 mo1 mo2 Thermodynamic theory Chemical potential of the solvent: mo1 = moo + RT ln xo1 Vpm: parcial molar volume
p1 p2 mo1 mo2 Equilibrium: mo1 = mo2 mo1 = moo + RT ln xo1 + Vpmp1 mo2 = moo + RT ln xo2 + Vpmp2
mo1 = moo + RT ln xo1 + Vpmp1 mo2 = moo + RT ln xo2 + Vpmp2 xo2 RT p2 – p1 = ln xo1 Vpm p = mo1 = mo2
RT xo2 p = ln xo1 Vpm One compartment is pure solvent (xo1=1) The solution is incompressible (Vpm=konstans) Solvent concentration is low = c (concentration of the solute) Vant’Hoff’s law: p = RTc
Molality: The number of moles of solute in 1 kg of solvent p = RTc Molarity: The number of moles of solute in 1 kg of solution
Ozmolarity = =molarity x number of dissociated ions 0,3 M glicerin: 0,3 Osmol 0,6 Osmol 0,3 M NaCl (Na+, Cl-):
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
Human and animal cells Plant cells Isotonic solution Hypotonic solution Hypertonic solution
Thermoosmosis Equal concentrations (at start) Cold Warm Dilution concentration Solvent transport fom the warmer to the cooler side
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 p = s RTc „reflection” coefficient 0 < s < 1 • Colloid osmotic pressure • Membrane is permeable to the solvent
Dp Szemipermeable membrane s = 1 Hidrostatic pressure difference „Leaky” membrane s < 1 Time „leaky”: permeable to the solvent
DV Shrinking (water uptake) Volume regulation Ion transport, release of isotonic solution Change of cell volume Time Volume regulation of living animal cells
Jk = Lk1 X1 + Lk2 X2 + … + Lkn Xn k = 1, 2, 3, …n Jv = LppDp + LpdDp Jd = LpdDp + LddDp Flow maintained by thermodynamic forces: Onsager equations: Jv: „volume” flow Jd: diffussion (osmotic) flow
JQ Dp Jv Thermoosmosis DT Dc Jm Je DU Diffusion Volume flow Heat flow Pressure difference Concentration difference Temperature difference Elektric potencial difference Electric current Mass transport
CyC Q + + Cytochromsystem ATP ATP Synthase I II O2 ADP NADH NAD+ OH- III OH- ADP ATP Chemiosmosis
CyC Q + + Citokróm rendszer ATP ATP Synthase I II O2 ADP NADH NAD+ OH- III OH- ADP ATP Ca2+ No “Mitochondrial Permeability Transition Pore” +Cy A
Membrare potencial in mitochondria Intact Damaged
Limited and Facilitated Diffusion Additional cellular transport mechanisms
Passive transport (simple diffusion) Facilitated diffusion Cell membrane Lipid bilayer Membrane proteins
Special, diffusion associated cellular mechanisms Chemotaxis: 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
Running: flagella turn counterclockwise „Tumbling”: flagella turn clockwise Random walking on organelle scale.