Membranes and Sensory Transduction

1 Membranes: Structure and Function.- 1. The Dynamic Structure of Cell Membranes.- 1.1. Introduction.- 1.2. Chemical Components.- 1.3. Membrane Structural Framework.- 1.4. Danielli-Davson and Fluid Mosaic Models.- 1.5. Laboratory Models.- 2. Kinetic and Thermodynamic Approach to Membrane Transport Properties.- 2.1. Equilibrium State.- 2.2. Nonequilibrium States.- 2.3. The Nernst-Planck Flux Equations.- 2.4. Specific Cases.- 2.5. Partition Coefficient at an Oil-Water Interface.- 2.6. Electrostatic Potentials at a Membrane-Solution Interface...- 2.7. Dipoles at a Membrane-Solution Interface.- 2.8. The Eyring Theory.- 3. Transport in Excitable Membranes.- 3.1. Introduction.- 3.2. Description of the Ionic Currents.- 3.3. The Hodgkin-Huxley Model.- 3.4. Ionic Channels.- 3.5. Selective Binding and Selective Permeability.- 3.6. The Sodium Channel.- 3.7. The Potassium Channel.- 3.8. Gating Currents.- 3.9. Noise Analysis.- 3.10. Single-Channel Recordings.- 3.11. Electrically Gated Channels in Planar Lipid Bilayers.- 3.12. Ionic Carriers in Planar Lipid Bilayers.- 4. Model Photosensitive Membranes.- 4.1. Introduction.- 4.2. Chlorophyll-Containing Lipid Bilayers.- 4.3. Bacteriorhodopsin and the Purple Membrane.- 4.4. Rhodopsin in Model Membranes.- References.- 2 Biochemistry of Chemosensory Behavior in Prokaryotes and Unicellular Eukaryotes.- 1. Diversity and Unity in Chemotaxis.- 1.1. Diverse Roles of Chemosensory Responses.- 1.2. Response-Regulator Model.- 2. Perception of Chemicals.- 2.1. Sensing the Gradient.- 2.2. Chemoreceptor Proteins on the Surface of Bacteria.- 2.3. Internal Receptors in Bacteria.- 2.4. Chemoreceptors in Eukaryotes.- 3. Signal Transduction.- 3.1. Focusing the Signals in Bacteria.- 3.2. Mechanism of Excitation in Paramecium.- 3.3. Signal Transduction in Leukocytes and Dictyostelium.- 4. Behavioral Responses.- 4.1. Klinokinesis in Bacteria.- 4.2. Klinokinesis and Orthokinesis in Ciliates.- 4.3. Tactic Behavior.- 5. Adaptation and Signal Processing.- 5.1. Role of Adaptation in Sensory Responses.- 5.2. Biochemistry of Adaptation in Bacteria.- 5.3. Adaptation in Eukaryotes.- 6. Models for Chemotaxis.- 7. Conclusion.- References.- 3 Mechanosensory Transduction in Protozoa.- 1. Introduction.- 2. Depolarizing and Hyperpolarizing Membrane Responses to Mechanical Stimulation.- 3. Ionic Mechanisms of the Mechanoreceptor Responses.- 4. Kinetic Analysis of the Mechanoreceptor Currents.- 5. Topographical Distribution of the Mechanoreceptor Channels.- 5.1. Ciliary Membrane or Somatic Membrane?.- 5.2. Anteroposterior Distribution.- 5.3. Dorsoventral Distribution.- 5.4. Species-Dependent Differences in Mechanosensitivity.- 6. Coupling of the Mechanoreceptor Responses with the Behavioral.- Responses.- References.- 4 Temperature Sensing in Microorganisms.- 1. Introduction.- 1.1. Overview.- 1.2. Difficulties Peculiar to Thermosensing.- 2. Cellular Components or Processes Affected by Temperature.- 2.1. Enzymes.- 2.2. Membranes.- 2.3. Protein-Lipid Interactions.- 2.4. Membrane Lipid Composition.- 3. Biological Examples.- 3.1. Bacteria.- 3.2. Ciliates.- 3.3. Acellular Slime Molds.- 3.4. Cellular Slime Molds.- 3.5. Nematodes.- 4. Summary.- References.- 5 Microbial Geotaxis.- 1. The Phenomena of Geotaxis.- 1.1. Geotaxis and Geotropism.- 1.2. Occurrence of Geotaxis.- 1.3. Orientation Direction Provided by Gravity.- 1.4. Energetics of Geotaxis.- 1.5. Biological Significance of Geotaxis.- 1.6. Geotaxis and Other Behaviors.- 2. Arenas of Debate.- 2.1. Mechanics versus Mechanism.- 2.2. Mechanisms of Response.- 2.3. Unproved Existence of Gravireceptors for Geotaxis.- 2.4. Involvement of Membranes and Sensory Transduction.- 3. Methods of Assessment.- 4 Hypotheses on the Mechanism of Geotaxis.- 4.1. Old Mechanisms and New Disputes.- 4.2. Physical Mechanisms.- 4.3. Physiological Mechanisms.- 5. Discussion.- 5.1. Physical and/or Physiological Mechanisms?.- 5.2. Conjectures on Physiological Mechanisms.- 5.3. Conclusion.- References.- 6 Photosensory Responses in Freely Motile Microorganisms.- 1. Introduction.- 2. Photomotile Responses.- 3. Photoreceptor Properties.- 3.1. Microenvironment and Photophysical Characteristics.- 3.2. Primary Molecular Events.- 4. Signal Transduction.- 4.1. Proton Gradients.- 4.2. Ionic Gradients.- 4.3. Electrical Gradients.- 4.4. Enzymatic Reactions.- 5. Information Transmission.- 5.1. Transmitter Molecules.- 5.2. Electrical Signals.- 6. Motor Responses.- 6.1. Flagellated Bacteria.- 6.2. Gliding Movements.- 6.3. Eukaryotic Cilia and Flagella.- 7. Concluding Remarks.- References.- 7 Phototropism.- 1. Introduction.- 2. The Sensory Transduction Chain.- 2.1. What Is It?.- 2.2. Elementary Rules for Model Builders.- 3. Phototropism in Higher Plants.- 3.1. Fluence-Response Curve.- 3.2. Phototropism and Light-Growth Response.- 3.3. Light Perception.- 3.4. Stimulus Transmission.- 4. Phototropism in Lower Plants.- 4.1. Types of Phototropic Reactions.- 4.2. Algae.- 4.3. Liverworts and Mosses.- 4.4. Ferns.- 4.5. Fungi.- 5. Quest for the Photoreceptor Responsible for Phototropism.- 5.1. Criteria for Identifying the Photoreceptor Suggested by Physiological Studies.- 5.2. The Action Spectrum Approach.- 5.3. The Inhibitor Approach.- 5.4. The Genetic Approach.- 5.5. The LIAC Approach.- 5.6. The Physicochemical Approach.- References.- Selected Readings.- 8 Chloroplast Movement.- 1. Introduction.- 2. Perception of the Light Signal.- 2.1. Photoreceptor Pigments in Photodinesis.- 2.2. Photoreceptor Pigments in Chloroplast Reorientation.- 2.3. Perception of Light Direction.- 3. Mechanics of Movement.- 4. Transduction Processes.- 4.1. The ATP Hypothesis.- 4.2. The Glyoxylate Hypothesis.- 4.3. The Proton Hypothesis.- 4.4. The Calcium Hypothesis.- 5. General Conclusions.- References.