Beschreibung
This Volume forms the cornerstone of this series of four books on Membrane Transport in Biology. It includes chapters that address i) the theoretical basis of investigations of transport processes across biological membranes, ii) some of the experimental operations often used by scientists in this field, iii) chemical and biological properties common to most biological membranes, and iv) planar thin lipid bilayers as models for biological membranes. The themes developed in these chapters recur frequently throughout the entire series. Transport of molecules across biological membranes is a special case of diffu sion and convection in liquids. The conceptual frame of reference used by investigators in this field derives, in large part, from theories of such processes in homogeneous phases. Examples of the application of such theories to transport across biological membranes are found in Chapters 2 and 4 of this Volume. In Chapter 2, Sten-Knudsen emphasizes a statistical and molecular approach while, in Chapter 4 Sauer makes heavy use of the thermodynamics of irreversi ble processes. Taken together, these contributions introduce the reader to the two sets of ideas which have dominated the thinking of scientists working in this field. Theoretical consideration of a more special character are also included in several other Chapters in Volume I. For example, Ussing (Chapter 3) re-works the flux ratio equation which he introduced into the field of transport across biological membranes in 1949.
Autorenporträt
Inhaltsangabe1 - Membrane Transport in Biology.- 2 - Passive Transport Processes.- A. Introduction.- B. Fundamental Definitions.- I. Flux.- II. Types of Passive Transport.- 1. Diffusion.- 2. Migration.- 3. Convection.- III. Flux Equations.- 1. Migration Flux.- 2. Convection Flux.- 3. Diffusion Flux.- a) Fick's Law.- b) The Driving Force behind the Diffusion Process.- 4. Diffusion and Migration Proceeding Concurrently.- 5. Convection with Superimposed Diffusion.- C. Diffusion Processes: Macroscopic Treatment.- I. The Diffusion Equation.- 1. Classification of Diffusion Processes.- II. Stationary Processes in One Dimension.- 1. Steady-State Diffusion in a Plate.- 2. The Permeability Coefficient.- 3. Stationary Diffusion through Two Different Media.- III. Time-Dependent Processes.- 1. Kinetics of Exchange between Two Phases Separated by a Membrane.- a) One of the Phases is Infinitely Large.- (i) Outer Concentration Zero.- (ii) Outer Concentration Finite, Inner Concentration Initially Zero.- b) Both Phases Comparable in Size.- c) Unidirectional Fluxes.- 2. Instantaneous Point Source (Green's Function).- a) Solutions of Diffusion Problems by Means of Green's Function.- (i) Initial Uniform Distribution in the One Half-Space.- (ii) The One Half-Space is Separated by an Impermeable Wall.- (iii) The Presence of an Absorbing Barrier.- (iv) Variable Flux into the Half-Space.- 3. Diffusion Out of a Plate.- a) Concentration Profiles.- b) The Time Constant for the Exchange of the Mean Concentration.- 4. Establishing the Stationary Concentration Profile.- D. Diffusion Processes: Microscopic Aspects.- I. Brownian Movements.- II. Smoluchowski's Treatment.- 1. Statistical Interpretation of the Diffusion Equation.- 2. Random Walk in One Dimension.- 3. The Einstein-Smoluchowski Equation.- III. Random Walk and Fick's Law (Einstein).- IV. The Smoluchowski Equation.- V. Kramers'Equation.- VI. Diffusion Coefficient and Mobility.- 1. Einstein's Relation.- 2. Einstein-Stokes' Relation.- E. Diffusion and Superimposed Convection.- I. The Equation of Motion.- II. Steady-State Concentration Profile.- 1. Stationary Transport through a Membrane.- a) Determination of the Flux.- b) Unidirectional Fluxes and Flux Ratio.- c) The Concentration Profile.- F. Electrodiffusion.- I. Conductance.- II. The Nernst-Planck Equations.- 1. Various Equivalent Forms.- 2. The Poisson Equation.- a) Electroneutrality.- b) The Constant Field.- III. Membrane Equilibrium.- 1. Nonosmotic Equilibrium.- a) The Nernst Equation.- b) Equivalent Electrical Circuit for the Ion-Selective Membrane.- 2. Donnan Equilibrium.- a) Thermodynamic Treatment.- b) Concentration and Potential Profiles between the Phases (The Poisson-Boltzmann Equation).- IV. Diffusion Potentials.- 1. Charging Time and Redistribution Time.- 2. The Henderson Regime.- 3. The Planck Regime.- a) Planck's General Relations.- b) The Electrical Equivalent Circuit for the Planck Regime.- c) Planck's Expression for the Diffusional Potential.- V. Electrodiffusion through Membranes.- 1. Single Salt.- a) Diffusion Potential.- b) Membrane Resistance.- c) Equivalent Electrical Circuit.- d) Electroneutrality.- 2. Ion-Selective Membrane.- 3. Membrane Separating Electrolytes Having a Common Ion.- a) Flux Ratio.- b) The Goldman Regime.- (i) The Separate Ionic Currents and the Diffusion Potential.- (ii) Total Membrane Current and Membrane Potential.- (iii) Concentration Profiles and Membrane Potential.- (iv) Ionic Conductances and Membrane Potential.- c) Equivalent Electrical Circuits.- Acknowledgements.- List of Symbols.- References.- 3 - Interpretation of Tracer Fluxes.- A. Introduction.- B. Fundamental Concepts.- C. Tracer Permeability Coefficients.- I. Measurement of Tracer Permeability Coefficients.- II. Multicompartment Systems.- D. The Concept of Unidirectional Flux.- I. Unidirectional Fluxes.- II. Isotope Effects.- III. Associated Unidirectional Fluxes.- IV. The Relation of Tracer Fluxes to Active and Passive Transport.- V. Effects of Membrane P
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