Modern Engineering Thermodynamics

CHAPTER 17
Thermodynamics of Biological Systems
CONTENTS
17.1 Introdução (Introduction) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693
17.2 Living Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693
17.3 Thermodynamics of Biological Cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695
17.4 Energy Conversion Efficiency of Biological Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 699
17.5 Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702
17.6 Thermodynamics of Nutrition and Exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705
17.7 Limits to Biological Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 711
17.8 Locomotion Transport Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714
17.9 Thermodynamics of Aging and Death . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 716
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 721
17.1 INTRODUÇÃO (INTRODUCTION)
Over the years, thermodynamics has remained essentially an engineering discipline with only infrequent
applications elsewhere. In chemistry, courses entitled Physical Chemistry specialize in applying thermodynamics
to chemical systems of the type treated in Chapter 15 of this book. Only recently has the developing
field of bioengineering begun to apply the macroscopic mass, energy, and entropy balance concepts of classical
thermodynamics to living systems. In this chapter, the results of applying these basic laws of thermodynamics
to biological systems are reviewed. The conclusions reached will help you understand how your body
functions and give you some insight into the operation of the complex molecular phenomena necessary to
sustain life on this or any other planet.
In this chapter, the basic thermodynamics of simple living systems (biological cells) is followed by discussions
of animal biological energy conversion efficiency, metabolism, nutrition, and exercise. Then, the fascinating
subjects of the limits to biological growth and an engineering view of living system mobility are presented. The
chapter ends, appropriately, with a thermodynamic discussion of biological aging and death. In this section, an
attempt is made to describe how and why living systems age differently from nonliving systems.
17.2 LIVING SYSTEMS
Only in the past few years has science begun to realize how the evolution of life is completely compatible with
the laws of physics. A key to this understanding has been the entropic explanation of self-organizing systems
and the connection between self-organization and energy flow. Self-organization can exist in both living and
nonliving systems, but living systems are self-organizing and self-replicating. The origin of life is apparently not
Modern Engineering Thermodynamics. DOI: 10.1016/B978-0-12-374996-3.00017-8
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