Quantitative Physiology: Cells and Tissues Lecture 2: September 8, 2006(Volume 1: 3.1-3.1.3; 3.2-3.2.2)IntracellularExtracellularMembranePumpsDissolutionand diffusionthroughlipid bilayerTransportthroughwaterchannelsTransportthroughgated ionchannelsCarrier-mediatedtransportFigure 2.19Fourier: heat fluxAnalogous flux lawsd (temperature)dxαOhm: currentd (potential)dxαFick: substance fluxd (concentration)dxαvolume Vamount of substance in VVconcentration c(x,t) = limV 0→Concentration at a pointin space and timewindowarea Aφ(x,t)amount of substance flowingthrough test window A in ∆tA∆tflux φ(x,t) = limA 0→∆t 0→Flux at a pointin space and timeFick's First Law• number of solute particles << number of solvent particles• motion of solute determined by collisions with solvent (ignore solute-solute interactions)• focus on 1 solute particle, assume motions of others are statistically identicalEvery τ seconds, solute particle gets hit by solvent particle.In response, solute particle is equally likely to move +l or −l.τ = mean free time; l = mean free pathx0 l 2l 3lRandom Walk Modelarea Random Walk Model → Fick's First
View Full Document
Unlocking...