414
9 Bioenergetics
• Hall Effect: An electric current in a material in the presence of a magnetic field
can induce a transverse electric field: ∇φ E = κ H B × J q .
• Nernst Effect: A flow of heat in a material in the presence of a magnetic field can
induce a transverse electric field: ∇ E = κ N B × J u .
• Ettinghausen Effect: An electric current in a material in the presence of a
magnetic field can induce a transverse gradient in temperature: ∇(1/T ) =
κ E B × J q .
• Righi-Leduc Effect: A flow of heat in a material in the presence of a magnetic
field can cause a transverse gradient of temperature: ∇(1/T ) = κ R B × J u .
9.24 Irreversible Thermodynamics
The study of biological systems using principles of thermodynamics is justified by
the fact that thermodynamic variables such as temperature and pressure can often
be defined for local but still macroscopic parts of an organism.
Investigating the properties of open systems which are globally far from equilibrium, Prigogine 73 observed that in certain cases order can be spontaneously created
within the system as the environment becomes more disordered. Examples include
crystallization, hurricanes, some chemical reactions with autocatalysis which run
in cycles instead of reaching fixed concentrations, and life itself. Thermal systems
can self-generate material flows. Systems which evolve to have subsystems which
have greater order than initially, and which accelerate the ordering process, are
called “self-organizing.” A necessary requirement for continued ordering is a flow
of energy into and out of the system. During the process of ordering for cyclic
processes in an open system, entropy production in the environment implies that
the processes are ‘irreversible’. This is both a statistical statement (i.e. it should
read, “highly improbable”) and a statement about information loss caused by the
practical inability to track the dynamics of microstates. We will return to this topic
in the chapter on ordering theory (Chap. 15.)
9.25 On the Evolution of Driven Systems
Biological systems are not in thermodynamic equilibrium. They contain ordered
structures holding energy. If there is no flow of energy into the system from the
environment, those ordered structures will eventually disassociate. After all, having
been created by interactions, the ordered structures can decay through interactions,
73 I. Prigogine, Thermodynamics of Irreversible Processes, Second Edition, [Wiley] (1961);
Gregoire Nicolis and Ilya Prigogine, Self-Organization in Non-Equilibrium Systems, [Wiley]
(1977).
9 Bioenergetics
• Hall Effect: An electric current in a material in the presence of a magnetic field
can induce a transverse electric field: ∇φ E = κ H B × J q .
• Nernst Effect: A flow of heat in a material in the presence of a magnetic field can
induce a transverse electric field: ∇ E = κ N B × J u .
• Ettinghausen Effect: An electric current in a material in the presence of a
magnetic field can induce a transverse gradient in temperature: ∇(1/T ) =
κ E B × J q .
• Righi-Leduc Effect: A flow of heat in a material in the presence of a magnetic
field can cause a transverse gradient of temperature: ∇(1/T ) = κ R B × J u .
9.24 Irreversible Thermodynamics
The study of biological systems using principles of thermodynamics is justified by
the fact that thermodynamic variables such as temperature and pressure can often
be defined for local but still macroscopic parts of an organism.
Investigating the properties of open systems which are globally far from equilibrium, Prigogine 73 observed that in certain cases order can be spontaneously created
within the system as the environment becomes more disordered. Examples include
crystallization, hurricanes, some chemical reactions with autocatalysis which run
in cycles instead of reaching fixed concentrations, and life itself. Thermal systems
can self-generate material flows. Systems which evolve to have subsystems which
have greater order than initially, and which accelerate the ordering process, are
called “self-organizing.” A necessary requirement for continued ordering is a flow
of energy into and out of the system. During the process of ordering for cyclic
processes in an open system, entropy production in the environment implies that
the processes are ‘irreversible’. This is both a statistical statement (i.e. it should
read, “highly improbable”) and a statement about information loss caused by the
practical inability to track the dynamics of microstates. We will return to this topic
in the chapter on ordering theory (Chap. 15.)
9.25 On the Evolution of Driven Systems
Biological systems are not in thermodynamic equilibrium. They contain ordered
structures holding energy. If there is no flow of energy into the system from the
environment, those ordered structures will eventually disassociate. After all, having
been created by interactions, the ordered structures can decay through interactions,
73 I. Prigogine, Thermodynamics of Irreversible Processes, Second Edition, [Wiley] (1961);
Gregoire Nicolis and Ilya Prigogine, Self-Organization in Non-Equilibrium Systems, [Wiley]
(1977).