Chapter 9
Bioenergetics
For those who want some proof that physicists are human,
consider the idiocy of all the different units which they use for
measuring energy.
—Richard Feynman
Summary The activity of life requires a flow of energy into and out of the life
system. Because life systems maintain and add to their internal order, the energy
source may allow an ‘entropy’ flow into the life system, and, in turn, the energy
flow out must carry entropy into the environment. The concepts of temperature,
heat, and entropy are defined in the subject of thermodynamics, at first developed
in the 1800s through macroscopic observational principles, but now is supported by
the physics and statistics of a large number of molecules in microscopic interaction.
This chapter emphasizes the macroscopic behavior of thermal systems, including
phase changes, osmosis, diffusion, active transport across cell membranes, and
biochemical reactions. The next chapter gives the statistical arguments behind
thermodynamics, with applications to cellular systems.
9.1 Biology and Energy Flow
Life, having replication capabilities, must be able to generate order from more
disordered states. 1 Microscopic dynamics and statistical ideas are sufficient to
understand how open subsystems naturally become more ordered, and to understand
the limitations to the amount of order which can be expected. These ideas are
also able to explain how energy spontaneously flows through open systems, which
includes all life forms, if the ‘sources’ of energy are more ordered than the ‘sinks’.
Individual organisms become more ordered by building internal structures. This
means the organism necessarily must release heat into its environment.
1 As we will see, order is a measurable quantity.
© Springer Nature Switzerland AG 2020
W. C. Parke, Biophysics, https://doi.org/10.1007/978-3-030-44146-3_9
325
Bioenergetics
For those who want some proof that physicists are human,
consider the idiocy of all the different units which they use for
measuring energy.
—Richard Feynman
Summary The activity of life requires a flow of energy into and out of the life
system. Because life systems maintain and add to their internal order, the energy
source may allow an ‘entropy’ flow into the life system, and, in turn, the energy
flow out must carry entropy into the environment. The concepts of temperature,
heat, and entropy are defined in the subject of thermodynamics, at first developed
in the 1800s through macroscopic observational principles, but now is supported by
the physics and statistics of a large number of molecules in microscopic interaction.
This chapter emphasizes the macroscopic behavior of thermal systems, including
phase changes, osmosis, diffusion, active transport across cell membranes, and
biochemical reactions. The next chapter gives the statistical arguments behind
thermodynamics, with applications to cellular systems.
9.1 Biology and Energy Flow
Life, having replication capabilities, must be able to generate order from more
disordered states. 1 Microscopic dynamics and statistical ideas are sufficient to
understand how open subsystems naturally become more ordered, and to understand
the limitations to the amount of order which can be expected. These ideas are
also able to explain how energy spontaneously flows through open systems, which
includes all life forms, if the ‘sources’ of energy are more ordered than the ‘sinks’.
Individual organisms become more ordered by building internal structures. This
means the organism necessarily must release heat into its environment.
1 As we will see, order is a measurable quantity.
© Springer Nature Switzerland AG 2020
W. C. Parke, Biophysics, https://doi.org/10.1007/978-3-030-44146-3_9
325