52
RICE UNIVERSITY STUDIES
Summary
The reaction system which 1 have described mathematically has the
following features: 1 ) It is determined when fuel, oxidant, phosphate, and
ADP concentrations are given, i. e., the rates and all intermediate
concentrations are set; 2) By proper choice of constants the system rate
can be made insensitive to oxygen and substrate concentrations, and
sensitive to phosphate and/or ADP concentrations; 3) The transient
response of the system to changes in external conditions can be made
rapid (on the order of the reaction time scale mentioned earlier); and 4)
Changes in the level of activity can be governed by alterations in the
source-loss ratio (rs∕M), with characteristic response time much longer
than the reaction time scale.
Some of the details of the qualitative behavior of the system will be
discussed in the next paper. Before I turn my system over to the analog
computer, I might interject a skeptical word about using this model to
fit real system data. In writing a general kinetic scheme for the Krebs
cycle and the Electron Transport scheme, 1 have necessarily introduced
a large number of constants. It might be tempting to try to use this array
of adjustable parameters to force a fit with a particular set of data for a
bacterial population. Unless the data represented individual cell
metabolism rates using a single substrate, this would clearly be misuse
of the model.
NOTES
1. If diffusion is only a contributing rather than a limiting factor, its effect can be absorbed
in the kinetics to be presented.
2. This also explains how the cycle can get started in the first place.