CHAPTER ONE Thermal Effects and Sensitivity of Biological Membranes Le on D. Islas Department of Physiology, School of Medicine, National Autonomous University of Mexico (UNAM), Mexico City, Mexico E-mail: islas@liceaga.facmed.unam.mx Contents 1. Introduction 1 2. Response of Organisms to Changes in Temperature 2 2.1 Worms and flies 2 2.2 Bacteria 4 3. General Thermal Dependence of Membrane Properties 5 3.1 Role of membrane fluidity 5 3.2 Membrane electrical properties and temperature 7 4. Pyroelectricity 9 5. Infra Red Radiation and Capacitance 10 6. Activation of Specific Channels by IR 12 7. Conclusions 13 Acknowledgments 13 References 13 Abstract Temperature is one of the key parameters that controlled the origin and evolution of life on earth and it continues to be a principal regulator of the functions of organisms. Some aspects of the response of simple and complex organisms to temperature vari- ations are encoded in the physical properties of the cell components, with the all- important plasma membrane playing a principal role. Other responses to temperature are more specific and through evolution, specialized receptors with particular temper- ature sensitivities have appeared to mediate this signaling. While some of these recep- tors are ancient and can be found in very primitive organisms, it seems that the mechanisms used by prokaryotes and eukaryotes are very different, indicating that tem- perature sensitivity has evolved in more than one occasion during evolution. 1. INTRODUCTION Ambient temperature is one of the most important parameters that make life on earth possible. At the same time, the existence of temperature Current Topics in Membranes, Volume 74 ISSN: 1063-5823 http://dx.doi.org/10.1016/B978-0-12-800181-3.00001-4 © 2014 Elsevier Inc. All rights reserved. 1 j