Thomas Fischer Weiss. Cellular Biophysics. Volume 1: Transport. A Bradford Book The MIT Press Cambridge, Massachusetts London, England

Transcription

1 Thomas Fischer Weiss Cellular Biophysics Volume 1: Transport A Bradford Book The MIT Press Cambridge, Massachusetts London, England

2 1996 Massachusetts Institute of Technology All rights reserved. No part of this publication may be reproduced in any form by any electronic or mechanical means (including photocopying, recording, or information storage and retrieval) without permission in writing from. the publisher. This book was set in Lucida Bright by Windfall Software using ZzT X and was printed and bound in the United States of America. library of Congress Cataloging-in-Publication Data Weiss, Thomas Fischer Cellular biophysics I Thomas Fischer Weiss v. <1- > ; em. Includes bibliographical references and index. Contents: v. 1. Transport- v. 2. Electrical properties. ISBN (v. 1).- ISBN (v. 2) 1. Cell physiology. 2. Biophysics. 3. Biological transport. 4. Electrophysiology. I. Title. QH63l.W '6041-dcZO RS WEI HD H CIP To Aurice B, Max, Elisa, and Eric

3 Contents Preface xix ix Units, Physical Constants, and Symbols xxvii 1 Introduction to Membranes 1 2 Introduction to Transport 49 3 Diffusion 83 4 Solvent Transport Concurrent Solute and Solvent Transport Carrier-Mediated Transport Ion Transport and Resting Potential Cellular Homeostasis 571 List of Figures 645 List of Tables 659 Contents of Volume Index 669

4 Preface xix Subject and Orientation of the Book Expected Background of the Reader A Note to the Instructor xx Preparation of the Manuscript Personal Perspective Acknowledgments References xxvi xxiv xxiii Units, Physical Constants, and Symbols Units xxvii xxi xxvii xix Base SI Units xxvii Derived SI Units xxvii Decimal Multiples and Submultiples of SI Units Commonly Used Non-SI Units and Conversion Factors xxviii Physical Constants xxix Fundamental Physical Constants xxix Physical Properties of Water xxix Atomic Numbers and Weights xxx Symbols xxxii References xxxv xx xxviii

5 xi X 1 2 Introduction to Membranes Historical Perspective Fundamental Concepts of Living Organisms Emerging Concepts of Cell Membranes Survey of Cell Structure Molecules Atoms, Elements, and Bonds Organic Molecules Cell Membrane Structure Contents of Membranes-Lipids, Proteins, and Carbohydrates The Ubiquitous Phospholipid Bilayer Membrane Fluidity Disposition of Membrane Proteins 40 Exercises 44 References 46 Introduction to Transport Introduction Cell Requirements Transport in the Body Illustrated Using a Potato Composition of a Potato Digestion of a Potato Structure of the Small Intestine Structure of Enterocytes Final Stage of Digestion Sugar Transport into and out of Enterocytes Sugar Transport into and out of the Circulatory System Sugar Transport into Cells and Utilization of Sugars 2.4 Cellular Transport Functions Maintenance of Intracellular Composition Water Homeostasis Secretion and Absorption Survey of Transport Mechanisms Methods for Studying Membrane Transport Physicochemical Methods Preparations Summary 79 Exercises 80 References 81 Diffusion Macroscopic Description Background Diffusion Variables Fick's First Law The Continuity Equation Fick's Second Law: The Diffusion Equation Diffusion with Convection and Chemical Reactions Postscript on Diffusion: The Second Law of Thermodynamics Microscopic Model Introduction The Microscopic Basis for Fick's First Law The Microscopic Space-Time Evolution of Particle Location: The Binomial Distribution The Macroscopic Space-Time Evolution of Particle Location: The Gaussian Distribution Concentration as a Statistical Average of the Number of Particles per Unit Volume The Diffusion Coefficient Solute in a Simple Fluid Solute in a Polymer Equivalent Diffusion "Force" Diffusion Processes Time-Invariant Diffusion Processes Time-Varying Diffusion Processes Membrane Diffusion Homogeneous Membranes Porous Membranes 124

6 xii xiii Two-Compartment Diffusion Derivation for a Thin Membraneh T1hi3? M mbrane Conditions for the Validity of t e n- e l 133 Approximation: A Specific Examp e 3.8 Measurements of Diffusion Through Cellular Membranes Overton's Rules Methods A Seminal Study The Dissolve-Diffuse Mechanism The Water Channel Hypothesis Appendix 3.1 Moments of the Binomial Distri~uti.on Appendix 3.2 Moments of the Gaussian Distnbutwn Appendix 3.3 Solution of the Homogeneous Diffusion Equation 156 Exercises 158 Problems 162 References 1 79 Solvent Transport Introduction Hydraulic Pressure Osmotic Pressure Historical Perspective The Van't Hoff Law of Osmotic Pressure Osmotic and Hydraulic Flow in Porous Media Differential Laws of Solvent Transport Conservation of Mass Steady-State Solvent Transport Steady-State Solvent Transport Through Thin Membranes Macroscopic Relations Microscopic Mechanisms of Water Transport for Simple Membrane Models The Physical Basis of Osmotic Pressure and Osmosis Some Proposed Mechanisms General Conclusions Concerning the Mechamsm of Osmotic Pressure and of Osmosis An Intuitive Explanation of Osmotic Pressure and Osmosis Primary Responses of Cells to Changes in Osmotic Pressure Osmotic Equilibrium of Cells Kinetics of Volume Changes of Cells in Response to Osmotic Pressure Changes The Complexity of Cellular Volume Control Molecular Mechanisms of Water Transport Through Cellular Membranes Osmotic and Diffusive Permeability of Membranes Molecular Biology of Water Channels Summary of Water Transport Mechanisms in Cell Membranes 247 Appendix 4.1 Thermodynamic Relations for an Ideal, Dilute Solution 248 Appendix 4.2 Poiseuille's Law 251 Exercises 253 Problems 258 References 2 72 Concurrent Solute and Solvent Transport Introduction Concurrent, Uncoupled Transport of Solute and Solvent Derivation of Equations Solutions for a Cell with Constant Surface Area Measurements Inadequacies of Uncoupled Flow Equations Conceptual Problems The Distinction Between Uncoupled and Coupled Transport Indistinguishable and Impermeant Solutes Diffusion and Convection Through a Porous Membrane: Indistinguishable Solute Derivation of Flux Equations The Linearized Equation of Coupled Flow for an "Indistinguishable" Solute 299

7 xiv XV The Kedem-Katchalsky Equations for Linear, Coupled Flow Through a Membrane Macroscopic Laws of Transport Microscopic Mechanisms of Transport of Water and a Permeant Solute in Simple Membrane Models 305 Coupled Solute and Solvent Transport for a Cell Theory Measurements Conclusions 315 Exercises 316 Problems 320 References 329 carrier-mediated Transport Introduction Distinguishing Characteristics The Notion of a Carrier 339 Chemical Reactions: A Macroscopic Description Chemical Reactions of Low Order Reaction Rates Discrete Diffusion Through Membranes carrier Models Simple, Symmetric, Four-State Carrier Model with One Solute Simple, Symmetric, Six-State Carrier Model With Two Ligands Introduction to Active Transport General, Four-State Carrier Model Other Carrier Models Hexose Transport in Cells Experimental Measurements and Methods for Estimatmg the Kinetic Parameters Applicability of Carrier Models to Measurements from Cells Conclusions Regulation of Glucose The Discovery of the Role of Insulin: A Historical Perspective Glucose Absorption, Utilization, Storage, and Control Summary Molecular Biology of Glucose Transporters Density of Glucose Transporters Isolation of the Glucose Transporter Structure of Glucose Transporters Exercises Problems Recruitment of Glucose Transporters by Insulin References 440 Ion Transport and Resting Potential Introduction The Importance of Ion Transport The Maintained Difference of Potential and Concentration Across Cellular Membranes Continuum Electrodiffusion Electrodiffusion Equations Electrodiffusive Equilibrium Condition Electroneutrality Steady-State Conditions The State of Intracellular Ions Macroscopic Model of Passive Ion Transport Derivation from Microscopic Models Properties of the Macroscopic Model Resting Potential of Uniform Isolated Cells Modell: A Single Permeant Ion (the Bernstein Model) Dependence of Resting Potential on Ion Concentration Model 2: Multiple Permeant Ions Model 3: Independent Passive Voltage-Gated Ion Channels Molecular Basis of Passive Ion Transport Through Channels 495

8 xvii xvi Instability of the Resting Potential Instability of the Cell Volume Active Ion Transport Model 4: Model of Resting Potential, Including Both Active and Passive Transport Properties of Active Transport of Ions by the Sodium- Potassium Pump (Na+ - K+)-ATPase Comparison of Active and Passive Transport 527 Appendix 7.1 The Goldman Constant Field Model 528 Derivation of the Voltage-Current Characteristic 529 Properties of the Voltage-Current Characteristic 530 The Unidirectional Flux Ratio 531 The Goldman Equation for the Resting Potential 532 Exercises 533 Problems 541 References Cellular Homeostasis Introduction Volume Regulation Background Volume Regulatory Responses Conclusions General Equations for Homeostasis Kinetic Equations Quasi-Equilibrium Equations Solutions of the Equations for Homeostasis Homeostasis for Simple Cell Models Solute Flux Equations Nonelectrolyte Solutes Ionic Solutes Summary Inventory of Homeostatic Mechanisms Transport Mechanisms Intracellular Solute-Binding/Release Mechanisms Transporter Regulatory Mechanisms Transport Mechanisms in Selected Cell Types Uniform Isolated Cells Cells in an Epithelium Electrically Excitable Cells General Comments on the Mechanisms of Volume Regulation 619 Exercises 622 Problems 624 References 635 List of Figures 645 List of Tables 659 Contents of Volume Index 669