60
HENRY EYRING, RICHARD P. BOYCE AND JOHN D. SPIKES
The first is recognized as Saxen's relationship which was first derived
with kinetic theory using a much more restrictive model. Unfortunately,
such methods do not yield explicit values for the coefficients but the
importance of the method lies in its ability to relate effects which may
appear to be independent.
This completes, for the time being, the brief excursion into some of
the ideas of "classical" irreversible thermodynamics. Much could be
said about the validity of the underlying assumptions (14-16), especially concerning the reciprocal relations. In general, the system
under consideration must be near equilibrium. Exactly how near the
equilibrium state the system must be, however, in order that the postulated linearity will suffice as an adequate approximation is not always
made clear. In diffusion and chemical reactions, for example, the approximations described above are almost never satisfactory. In these
cases, any attempt to improve the theory by relating the forces and
fluxes by a nonlinear equation renders the whole approach impractically cumbersome.
Recently, irreversible processes have been treated by absolute rate
theory (17). The results derived are found to continue to hold for
large departures from equilibrium in a range where the Onsager reciprocal relations are no longer applicable. After the section on rate theory
has been presented, we shall indicate the essential features of such a
treatment.
IV. Reaction Rates in Chemical and Biological Systems
Protoplasm in order to function properly must maintain a constant
chemical composition within rather narrow limits, which implies the
existence of a precise control over the rates of the many reactions involved in metabolism. If, for example, the rates of reactions supplying
energy to the organism decrease, the general metabolism and activity
will slow down. On the other hand, if energy supplying reactions take
place too fast, food will be oxidized faster than the organism can replenish its supply. The study of reaction rates is much more complicated than the study of thermodynamics since, in addition to a
knowledge of the initial and final states, we must also know the details
of intermediate products and reaction mechanisms.
A. EFFECT OF TEMPERATURE ON REACTION RATE
As a result of experience we know that, in general, rates of chemical
reactions increase as the temperature is raised. Biological reactions, of
course, behave in much the same way. The range of temperature over
which biological systems can exist in a metabolically active form is ex-
HENRY EYRING, RICHARD P. BOYCE AND JOHN D. SPIKES
The first is recognized as Saxen's relationship which was first derived
with kinetic theory using a much more restrictive model. Unfortunately,
such methods do not yield explicit values for the coefficients but the
importance of the method lies in its ability to relate effects which may
appear to be independent.
This completes, for the time being, the brief excursion into some of
the ideas of "classical" irreversible thermodynamics. Much could be
said about the validity of the underlying assumptions (14-16), especially concerning the reciprocal relations. In general, the system
under consideration must be near equilibrium. Exactly how near the
equilibrium state the system must be, however, in order that the postulated linearity will suffice as an adequate approximation is not always
made clear. In diffusion and chemical reactions, for example, the approximations described above are almost never satisfactory. In these
cases, any attempt to improve the theory by relating the forces and
fluxes by a nonlinear equation renders the whole approach impractically cumbersome.
Recently, irreversible processes have been treated by absolute rate
theory (17). The results derived are found to continue to hold for
large departures from equilibrium in a range where the Onsager reciprocal relations are no longer applicable. After the section on rate theory
has been presented, we shall indicate the essential features of such a
treatment.
IV. Reaction Rates in Chemical and Biological Systems
Protoplasm in order to function properly must maintain a constant
chemical composition within rather narrow limits, which implies the
existence of a precise control over the rates of the many reactions involved in metabolism. If, for example, the rates of reactions supplying
energy to the organism decrease, the general metabolism and activity
will slow down. On the other hand, if energy supplying reactions take
place too fast, food will be oxidized faster than the organism can replenish its supply. The study of reaction rates is much more complicated than the study of thermodynamics since, in addition to a
knowledge of the initial and final states, we must also know the details
of intermediate products and reaction mechanisms.
A. EFFECT OF TEMPERATURE ON REACTION RATE
As a result of experience we know that, in general, rates of chemical
reactions increase as the temperature is raised. Biological reactions, of
course, behave in much the same way. The range of temperature over
which biological systems can exist in a metabolically active form is ex-