Nutrition and Health, 1992, Vol. 8, pp. 227-230 0260-1060/92 $10 © 1992 A B Academic Publishers, Printed in Great Britain
227
LETTER-ENERGY & LIFE Sir, In the inorganic world the two laws of thermodynamics rule supreme. They indicate that energy cannot of itself run up hill. The rules of entropy require it to disperse downhill. With living systems this is not the case. Structure intervenes. This is well illustrated by A.T.P. and by enzymes. "An active cell requires millions of molecules of A.T.P. per second to drive its biochemical machinery." 1 "Chemical changes, physical changes, and anything else you can think of all tend towards disorder (randomness )" 2 In spite of this the characteristic of the living system is its order. Its order, of course depends on its structure and function. It is this in which A.T.P. intervenes.
STRUCTURE
In the world without life some order does occur in the form of crystals. Atoms and molecules put themselves together. However such order differs from living order because it represents an incident in the downhill course of energy. It results from the attraction which oppositely charged ions have for one another. If enough are present, or if the water in which they are dissolved evaporates, crystals can form. However the order which results is not an order such as is manifested in the cell. There are, of course, other assemblies-within the planet earth; within the atmosphere; within the oceans. All are governed by entropy. When life first appeared on the planet, three or four billion years ago, an order inconsistent with the entropy of the second law of thermodynamics operated. Structure resulted from selection and assembly such as the construction of living systems requires. What is the energy here involved? Here we confront problems, not of life, but of the use of words. In spite of the second law of thermodynamics-the law of the randomness of energy, (its tendency to run downhill)-biologists speak of "free energy". This surely is a contradiction. Energy, as it runs downhill can be, and is, caught and bound. Moreover living systems are equipped with means-such as Downloaded from nah.sagepub.com at UCSF LIBRARY & CKM on April 24, 2015
228
A.T.P., enzymes and hormones whereby energy is directed up hill. By these means structure and order are realised. Free energy is a misleading term. Energy, when free, runs downhill. It is structure which secures that in living processes energy may in effect be made to operate uphill. This is illustrated when energy from the sun is captured and lodged in components of living systems, notably chloroplasts, and thereafter employed as what biologists have come to call "free energy", to order living structures and their functions. Energy is first bound and then employed as the structures ofliving systems require. This allows living order to be established on a planet where energy in general is seen to be entropic-disposed towards disorder. THE LIVING SYSTEM
To approach these problems it is interesting, first of all, to consider the frontier which separates any living system from its surroundings (from its environment). That frontier is the cell membrane reinforced by other structures. Second, to recognise traffic across that frontier consisting of constructional materials taken in and a selection which decides what must be cast out. THE FRONTIER OF LIFE
It is obvious that every living system has a boundary which delimits it, whilst at the same time providing a frontier across which it transacts its affairs so that it may obtain what it requires and expell that which it does not require. Such boundaries are membranous. Where did they come from? If now we cast our minds back to the era when there was no life on this planet-say some four billion years ago-and consider the living systems which first appeared (biologists tell us that they were prokaryotic cells) we may ask what the first living systems required in order to form a frontier within which living systems could be-first of all structured-and thereafter made to function. If we may judge by the present day prokaryotic cells which it would seem are the descendants of their prokaryotic ancestors-the answer would direct our attention to the bilipid layers of cell membranes. (We should, however, recollect that contemporary cells require protein structures to be added to these membranes). If we are seeking to understand how all this began-some four billion years ago-we have to decide how the highly complex cell membrane originated. This was, biologically considered, a very complex architectural achievement. Fatty acids had to be so arranged that, to begin with, a double (bilipid) layer had to be assembled and arranged in such a way that its effects Downloaded from nah.sagepub.com at UCSF LIBRARY & CKM on April 24, 2015
229
were "amphipathic" which is to say that one side of their arrangement was hydrophilic whilst the other side of the bilayer was hydrophobic. To achieve this was no mean architectural achievement and, of course, this was just a beginning. Other structures were introduced into cell membranes, notably proteins which had different chemical effects. How were these selected and introduced? It is manifest that these arrangements have been established. But how has this been achieved in a scene where the second law of thermodynamics operates? Surely some other principle was present to secure these effects. When such effects are taken to pieces it is evident how the pieces have fitted together. But how, in the beginning was the architectural construction achieved? If we reconsider that which our analysis ofliving systems presents us with, the architectural principle, which is seen to have been operative, cannot be deduced from either physics or chemistry although these disciplines show us what has happened after it has taken place. In addition to physics and chemistry which show us the products ofliving systems surely we need to enquire into the principle which set structures up and chose what was necessary to do so. Construction and selection are involved. What was chosen was, in the main, built out of carbon and hydrogen atoms with a little help from oxygen atoms. Often, as in palmitic, stearic, oleic and linoleic acid, there were 16 or 18 atoms of carbon and 30 to 36 atoms of hydrogen with just a couple of atoms of oxygen. It was not enough for these atoms to be distributed randomly. Somehow a precise, repeatable order was established, repeated and maintained. In this way amphipathic bilayers were assembled and repeated as required and the boundaries between living systems which maintained their order for a time, and the oceanic seas which, devoid of life, saw the first introduction whilst themselves being inorganically entropic-were established. Life had begun but it was to take a couple of billion years before structure and function evolved a more elaborate type of cell-a eukaryotic cell-and thereafter, as we say, evolve. Obviously what the limiting membrane of the cell does is to separate the living system from its environment by the bilipid layer of its limiting membrane. This membrane has the ability to take in some molecules from its environment (by endocytosis) and to cast others out from the area which the membrane surrounds in order to realise the cell (by exocytosis). This taking in and casting out is the basis of nutrition. Of course what is taken in has to be used to create or support the living system involved or if it cannot be selected and employed for this purpose, well! it is cast out. Of course, all this occurs within the confines of the membranous frontier which the cell, the living system, has set up. The question of the architect and the architectural principle which underpins all this remains to be studied and described. Downloaded from nah.sagepub.com at UCSF LIBRARY & CKM on April 24, 2015
230
NUTRITION
With the frontier of the cell we encounter nutrition which is much more extraordinary than is commonly recognised. The original inorganic world (which, although later modified by life, then had neither life nor membranous frontiers) was that on which living systems, when they originated, depended for their constructional materials. These were supplied by their nutrition, the origin of which lies in the endocytosis and the exocytosis which the cell achieves. What is not clear and what is taken for granted by science is the constructional (architectural) ability which operates in living systems. All living systems depend on nutrition. Once nutrition is operative we identify two territories-that which lies within living systems and the nonliving territory which surrounds them. When life started this non-living territory was not only devoid of life, it also had a chemistry which we now speak of as inorganic. Inorganic chemistry applies in the world without life; organic or biochemistry applies to living systems and their products. What we observe is that materials are selected from the inorganic world and used to create and support living systems. The entropy, described by the second law of thermodynamics, operates throughout. However, in order to have a frontier which serves the living system, atoms and molecules, instead of being distributed randomly (as entropy requires) are assembled. The bilipid layers of the frontiers of cells provide a dramatic illustration of this. The construction, and indeed the functions of bilipid layers, forming membranes, are only a beginning. A different kind of world-that of the living system-has means by which it creates intracellular structures-such as mitochondria, protoplasts and so on. And, of course, the real achievement of life is to have established the ability by which, after the living system has achieved its identity, it can not only reproduce itself but evolve. What nutrition emphasizes is that the living system needs to acquire the means by which it will construct itself in virtue of the powers which it possesses to do so. 1. The Science of Biology. William Purves & Gordon Orians. Sinauer Associates Inc. Sunderland, Massachusetts. p. 177. 2. Ditto p. 151.
*Kenneth Barlow Shouler's End Thorn borough Buckingham MK18 7DH
*Dr Barlow was founding editor of this journal. Downloaded from nah.sagepub.com at UCSF LIBRARY & CKM on April 24, 2015
227
LETTER-ENERGY & LIFE Sir, In the inorganic world the two laws of thermodynamics rule supreme. They indicate that energy cannot of itself run up hill. The rules of entropy require it to disperse downhill. With living systems this is not the case. Structure intervenes. This is well illustrated by A.T.P. and by enzymes. "An active cell requires millions of molecules of A.T.P. per second to drive its biochemical machinery." 1 "Chemical changes, physical changes, and anything else you can think of all tend towards disorder (randomness )" 2 In spite of this the characteristic of the living system is its order. Its order, of course depends on its structure and function. It is this in which A.T.P. intervenes.
STRUCTURE
In the world without life some order does occur in the form of crystals. Atoms and molecules put themselves together. However such order differs from living order because it represents an incident in the downhill course of energy. It results from the attraction which oppositely charged ions have for one another. If enough are present, or if the water in which they are dissolved evaporates, crystals can form. However the order which results is not an order such as is manifested in the cell. There are, of course, other assemblies-within the planet earth; within the atmosphere; within the oceans. All are governed by entropy. When life first appeared on the planet, three or four billion years ago, an order inconsistent with the entropy of the second law of thermodynamics operated. Structure resulted from selection and assembly such as the construction of living systems requires. What is the energy here involved? Here we confront problems, not of life, but of the use of words. In spite of the second law of thermodynamics-the law of the randomness of energy, (its tendency to run downhill)-biologists speak of "free energy". This surely is a contradiction. Energy, as it runs downhill can be, and is, caught and bound. Moreover living systems are equipped with means-such as Downloaded from nah.sagepub.com at UCSF LIBRARY & CKM on April 24, 2015
228
A.T.P., enzymes and hormones whereby energy is directed up hill. By these means structure and order are realised. Free energy is a misleading term. Energy, when free, runs downhill. It is structure which secures that in living processes energy may in effect be made to operate uphill. This is illustrated when energy from the sun is captured and lodged in components of living systems, notably chloroplasts, and thereafter employed as what biologists have come to call "free energy", to order living structures and their functions. Energy is first bound and then employed as the structures ofliving systems require. This allows living order to be established on a planet where energy in general is seen to be entropic-disposed towards disorder. THE LIVING SYSTEM
To approach these problems it is interesting, first of all, to consider the frontier which separates any living system from its surroundings (from its environment). That frontier is the cell membrane reinforced by other structures. Second, to recognise traffic across that frontier consisting of constructional materials taken in and a selection which decides what must be cast out. THE FRONTIER OF LIFE
It is obvious that every living system has a boundary which delimits it, whilst at the same time providing a frontier across which it transacts its affairs so that it may obtain what it requires and expell that which it does not require. Such boundaries are membranous. Where did they come from? If now we cast our minds back to the era when there was no life on this planet-say some four billion years ago-and consider the living systems which first appeared (biologists tell us that they were prokaryotic cells) we may ask what the first living systems required in order to form a frontier within which living systems could be-first of all structured-and thereafter made to function. If we may judge by the present day prokaryotic cells which it would seem are the descendants of their prokaryotic ancestors-the answer would direct our attention to the bilipid layers of cell membranes. (We should, however, recollect that contemporary cells require protein structures to be added to these membranes). If we are seeking to understand how all this began-some four billion years ago-we have to decide how the highly complex cell membrane originated. This was, biologically considered, a very complex architectural achievement. Fatty acids had to be so arranged that, to begin with, a double (bilipid) layer had to be assembled and arranged in such a way that its effects Downloaded from nah.sagepub.com at UCSF LIBRARY & CKM on April 24, 2015
229
were "amphipathic" which is to say that one side of their arrangement was hydrophilic whilst the other side of the bilayer was hydrophobic. To achieve this was no mean architectural achievement and, of course, this was just a beginning. Other structures were introduced into cell membranes, notably proteins which had different chemical effects. How were these selected and introduced? It is manifest that these arrangements have been established. But how has this been achieved in a scene where the second law of thermodynamics operates? Surely some other principle was present to secure these effects. When such effects are taken to pieces it is evident how the pieces have fitted together. But how, in the beginning was the architectural construction achieved? If we reconsider that which our analysis ofliving systems presents us with, the architectural principle, which is seen to have been operative, cannot be deduced from either physics or chemistry although these disciplines show us what has happened after it has taken place. In addition to physics and chemistry which show us the products ofliving systems surely we need to enquire into the principle which set structures up and chose what was necessary to do so. Construction and selection are involved. What was chosen was, in the main, built out of carbon and hydrogen atoms with a little help from oxygen atoms. Often, as in palmitic, stearic, oleic and linoleic acid, there were 16 or 18 atoms of carbon and 30 to 36 atoms of hydrogen with just a couple of atoms of oxygen. It was not enough for these atoms to be distributed randomly. Somehow a precise, repeatable order was established, repeated and maintained. In this way amphipathic bilayers were assembled and repeated as required and the boundaries between living systems which maintained their order for a time, and the oceanic seas which, devoid of life, saw the first introduction whilst themselves being inorganically entropic-were established. Life had begun but it was to take a couple of billion years before structure and function evolved a more elaborate type of cell-a eukaryotic cell-and thereafter, as we say, evolve. Obviously what the limiting membrane of the cell does is to separate the living system from its environment by the bilipid layer of its limiting membrane. This membrane has the ability to take in some molecules from its environment (by endocytosis) and to cast others out from the area which the membrane surrounds in order to realise the cell (by exocytosis). This taking in and casting out is the basis of nutrition. Of course what is taken in has to be used to create or support the living system involved or if it cannot be selected and employed for this purpose, well! it is cast out. Of course, all this occurs within the confines of the membranous frontier which the cell, the living system, has set up. The question of the architect and the architectural principle which underpins all this remains to be studied and described. Downloaded from nah.sagepub.com at UCSF LIBRARY & CKM on April 24, 2015
230
NUTRITION
With the frontier of the cell we encounter nutrition which is much more extraordinary than is commonly recognised. The original inorganic world (which, although later modified by life, then had neither life nor membranous frontiers) was that on which living systems, when they originated, depended for their constructional materials. These were supplied by their nutrition, the origin of which lies in the endocytosis and the exocytosis which the cell achieves. What is not clear and what is taken for granted by science is the constructional (architectural) ability which operates in living systems. All living systems depend on nutrition. Once nutrition is operative we identify two territories-that which lies within living systems and the nonliving territory which surrounds them. When life started this non-living territory was not only devoid of life, it also had a chemistry which we now speak of as inorganic. Inorganic chemistry applies in the world without life; organic or biochemistry applies to living systems and their products. What we observe is that materials are selected from the inorganic world and used to create and support living systems. The entropy, described by the second law of thermodynamics, operates throughout. However, in order to have a frontier which serves the living system, atoms and molecules, instead of being distributed randomly (as entropy requires) are assembled. The bilipid layers of the frontiers of cells provide a dramatic illustration of this. The construction, and indeed the functions of bilipid layers, forming membranes, are only a beginning. A different kind of world-that of the living system-has means by which it creates intracellular structures-such as mitochondria, protoplasts and so on. And, of course, the real achievement of life is to have established the ability by which, after the living system has achieved its identity, it can not only reproduce itself but evolve. What nutrition emphasizes is that the living system needs to acquire the means by which it will construct itself in virtue of the powers which it possesses to do so. 1. The Science of Biology. William Purves & Gordon Orians. Sinauer Associates Inc. Sunderland, Massachusetts. p. 177. 2. Ditto p. 151.
*Kenneth Barlow Shouler's End Thorn borough Buckingham MK18 7DH
*Dr Barlow was founding editor of this journal. Downloaded from nah.sagepub.com at UCSF LIBRARY & CKM on April 24, 2015
