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J O H N P A U L
pathways? 5. T o what extent are metabolic pathways influenced by
environmental factors and what light does this throw on regulatory
mechanisms within the cell? 6. D o all cells behave in the same way in
identical conditions of culture or do individual differences persist? In
particular, what significance attaches to the behaviour of cells originating from cancer tissue as compared with those derived from normal
tissue?
Before entering upon a discussion of these individual questions it is
proposed to consider some aspects of the bio-energetics of cultured cells
which are of general interest and have a direct bearing on many other
problems.
I I . E N E R G Y R E L A T I O N S H I P S IN G R O W I N G A N D
S T A T I O N A R Y C E L L S
Energy is required by animal cells for two main purposes, mechanical
work and biosynthetic processes.
A. M E C H A N I C A L W O R K
As is described elsewhere in this volume animal cells are capable of a
good deal of active movement. It has not yet proved possible to compute, even approximately, the energy requirements for such functions
as cellular migration, pinocytosis and cell division. Some other processes, such as the transport of substances into cells and the maintenance
of concentration gradients also require energy and in this instance we
can make estimates for at least one mechanism, the sodium pump.
Maizels, Remington and Truscoe (1958) have estimated that this takes
10-20°/o of the available energy of mouse ascites tumour cells. O n the
basis of figures kindly provided by Dr. Lamb for the ion flux in cultured
chick embryonic fibroblasts and, assuming an efficiency of three sodium
ions per A T P , the author has obtained a similar estimate. The energy
requirement for other transport processes is unknown but in view of
these figures we can guess that it is by no means negligible. It is not
possible at present to be more precise and we can only keep in mind
that in making estimates of energy requirements a margin of unknown
but appreciable size must be allowed for these functions.
B. B I O S Y N T H E T I C PROCESSES
Here we are on much sounder ground because so much is now known
of the energy changes in biochemical reactions that, given the chemical
composition of a biological structure, we can make a reasonable estimate of the amount of energy involved in synthesizing it from given
J O H N P A U L
pathways? 5. T o what extent are metabolic pathways influenced by
environmental factors and what light does this throw on regulatory
mechanisms within the cell? 6. D o all cells behave in the same way in
identical conditions of culture or do individual differences persist? In
particular, what significance attaches to the behaviour of cells originating from cancer tissue as compared with those derived from normal
tissue?
Before entering upon a discussion of these individual questions it is
proposed to consider some aspects of the bio-energetics of cultured cells
which are of general interest and have a direct bearing on many other
problems.
I I . E N E R G Y R E L A T I O N S H I P S IN G R O W I N G A N D
S T A T I O N A R Y C E L L S
Energy is required by animal cells for two main purposes, mechanical
work and biosynthetic processes.
A. M E C H A N I C A L W O R K
As is described elsewhere in this volume animal cells are capable of a
good deal of active movement. It has not yet proved possible to compute, even approximately, the energy requirements for such functions
as cellular migration, pinocytosis and cell division. Some other processes, such as the transport of substances into cells and the maintenance
of concentration gradients also require energy and in this instance we
can make estimates for at least one mechanism, the sodium pump.
Maizels, Remington and Truscoe (1958) have estimated that this takes
10-20°/o of the available energy of mouse ascites tumour cells. O n the
basis of figures kindly provided by Dr. Lamb for the ion flux in cultured
chick embryonic fibroblasts and, assuming an efficiency of three sodium
ions per A T P , the author has obtained a similar estimate. The energy
requirement for other transport processes is unknown but in view of
these figures we can guess that it is by no means negligible. It is not
possible at present to be more precise and we can only keep in mind
that in making estimates of energy requirements a margin of unknown
but appreciable size must be allowed for these functions.
B. B I O S Y N T H E T I C PROCESSES
Here we are on much sounder ground because so much is now known
of the energy changes in biochemical reactions that, given the chemical
composition of a biological structure, we can make a reasonable estimate of the amount of energy involved in synthesizing it from given