50
HENRY EYRING, RICHARD P. BOYCE AND JOHN D. SPIKES
storage and expenditure of free energy by organisms is independent of whether or not these organisms are in a steady state
condition or in equilibrium states. The evaluation of AF is often
based on the assumption that the system is in equilibrium when
in actuality it is not. Such values, then, must be examined carefully.
III. Thermodynamics of Open Systems
A. INTRODUCTION
Living systems avoid the death sentence of the Second Law by virtue of the fact that they are open systems. In this section we wish to
explore further the properties of open systems, in particular the steady
state, with the idea of indicating methods by which thermodynamic
analyses of such systems may be made.
B. ENTROPY COUPLING
In order to present this section in terms currently popular in the
literature, we will first consider some fundamental ideas that are attributed to de Donder (JO). He states the Second Law in the form
dq' = TdS - dq
(71)
where dq' is called the "uncompensated heat." Dividing through by T
gives
%-da-%
(72)
Providing that the process takes place within the system with the environment functioning solely as a heat reservoir, the quantity dq'/T is
the total amount of entropy created in the irreversible process dS iTr .
Assuming constant T and P
dq = dE + PdV
and
dS*-%-dS-(dB-PdV)Td8 -W-PdV)
(73)
Now
dF = dE + P dV - T dS
therefore
dSu T = —ψ—
(74)