#5 Metabolism without Enzymes and Cell Membranes?

Clay Catalysts

Metabolic processes within cells are catalysed by protein enzymes.  It was realized that the formation of macromolecules had to be catalysed by something, and unless life pulled itself up by its own bootstraps these catalysts could not be enzymes.  So, it was proposed by A.G. Caines-Smith in 1985 that clay composed of silicates was the catalyst of protometabolism (see footnote[1]). 

Proto-cell Membranes

It was soon realized that since the entire sea could not function as a metabolism, it had to be compartmentalized.  It was observed that cell membranes are composed of phospholipids that naturally form spheres when placed in water.  So, it was proposed that the protocell was bounded by a very simple lipid membrane that formed spontaneously.  The problem with this simple model is that the protocell would be isolated from its environment.  The phospholipid membrane of the hypothetical protocell would not allow molecules that fuel metabolism to enter the protocell, nor would it allow toxic waste products out.  Isolation from the environment spells non-viability for cells.

The cells we know have a phospholipid bilayer plasma membrane with both embedded and peripheral proteins that regulate the entry and exit of substances into and out of the cytoplasm.  The selectively permeable cell membrane maintains a steady internal environment within the cell.  Water and some small molecules can cross the phospholipid membrane and follow their concentration gradient, but larger molecules such as glucose and amino acids, and also ions are assisted across the membrane by carrier proteins that are specific to each molecule or ion.  Transmembrane proteins include channel proteins, carrier proteins, cell recognition proteins, receptor proteins and enzymatic proteins and transport may be active requiring the expenditure of energy donated by ATP.

The conclusion to this short section is that simple membranes would isolate a cell, making it unable to function as a cell, and complex membranes containing channels and carrier proteins that allow the cell to interact with its environment are complex.


[1] Cairns-Smith A.G.  (1985)  Seven Clues to the Origin of Life  Cambridge University Press; Cairns-Smith A.G. (1993) Genetic Takeover: And the Mineral Origins of Life Cambridge University Press

#4 Primeval Soup Theory

The Primeval Soup Theory for the origin of life on Earth was first proposed by J. B. S. Haldane (1892-1964), a British Marxist biologist who lived in the USA and Britain, and Alexander Oparin (1894-1980) of the USSR.  It is the idea that life arose from inorganic matter under conditions proposed as having existed on the early Earth, but not existing now.

There are various versions of the Primeval Soup Theory differing in some details.  All must include a reducing atmosphere since organic macromolecules will not form naturally without it.  Hence it is proposed that the atmosphere of the early Earth was composed of methane, ammonia and hydrogen.  There was a sea of water formed from condensed water vapour.  The energy which would trigger the emergence of life came from flashes of lightning, ultraviolet radiation or even meteorite impact.  The effect of the light or heat energy on the atmosphere of strange gases would be the formation of organic, carbon-based molecules that would accumulate in the water which thus became a prebiotic soup.

It is now known that if the early atmosphere was so reducing that it did not contain any carbon dioxide, then the Earth would have been covered with ice.  The discovery of the exotic world of hydrothermal vents then led to the hypothesis that life emerged in one of the places on Earth that had reducing conditions in a limited location.

The primeval soup would contain carbohydrates the components of sugars; amino acids the components of proteins; and nucleotides the components of DNA and RNA.  Thus, it is proposed in the Primeval Soup Theory that all the ingredients of life were present as building blocks on early Earth.  It has been observed that the building blocks of life do combine with each other in predictable ways.  At this point the Natural Selection argument is used to explain that little organic molecules (monomers) have an advantage if they become big organic molecules (polymers) and if they learn to self-replicate.  The survival of the fittest idea is applied to molecules, which form themselves into a protometabolism whose function is to form new types of molecules.  The idea of the evolution of macromolecules was proposed by Francis Crick and Leslie E. Orgel in 1973.

Robert Shapiro points out that the proposed compositions of the atmosphere of early Earth and the ‘soup’ are hypothetical, and may never have existed at all.  He also points out that the water of this ocean would prevent the formation of biological macromolecules since water prises nucleotides apart from each other by breaking sugar-phosphate bonds and severing bases from sugars (Shapiro 1986, pages 173-174).  Thus, DNA and RNA macromolecules in water become nucleotide small molecules.  Also, in the presence of water peptide polymers and proteins slowly break down into their amino acid components.

It seems that, whereas in the world of speculation, ‘Natural Selection’ as the driver builds up complex molecules, in the real world thermodynamics breaks down complex molecules into simpler ones.

#3 Origin of Life: Theory and Politics

As far as the history of ideas is concerned, the notion that life can arise from non-life was linked to the rise of Communism during the 20th century and its atheistic underpinning.  It was a necessary corollary to belief in Dialectical Materialism that Soviet scientists find an origin to life that did not involve God.  Thus, origin of life theories of the 20th century stepped forward hand in hand with the political ideals of the day.

Soviet scientists claimed that just as Marxism shows that history must drive itself forward towards the triumph of Communism, the beginnings of life drove itself forward towards the colonization of Earth by an imperative logic.  Soviet scientists believed that the cytoplasm of the cell contained the means of running the metabolism of the cell (just as the worker’s collectives supposedly ran the Soviet Union).  They hotly denied that the genetic material found in the nucleus of the cell contained the program for running the cell.  They claimed that the idea that the nucleus runs the cell was part of elitist ideology.  DNA had been discovered by scientists in Western Europe and was therefore denounced as a capitalist hypothesis. 

It seems that history had the last word, since genes did not go away and Communism fell.  However, the idea that life arose by chance or by some natural means that did not involve God remained in circulation and became part of the official dogma of NeoDarwinism. 

#2 Spontaneous Generation?

Historically nobody was much troubled by the origin of life.  The origin of life – where life came from – did not in the past really formulate itself as a question.  Quite apart from believing that the world has always been the way it is, and that God made it that way, it was commonly held that small forms of life simply came into existence spontaneously under certain conditions.

Spontaneous Generation is the belief that some living creatures arise suddenly by chance from matter independently of any parents.  Spontaneous Generation was accepted without dissent since ancient times until the second half of the 19th century.  It was thought that rotten meat turned into maggots, household dirt took on the form of Silverfish, while mould and bacterial colonies arise from damp corners.  Life simply appeared everywhere, all the time.  Nobody thought that the origin of life was a problem; it was only its persistent manifestation that was a problem.

The man who changed this situation was Louis Pasteur (1822-1895), French scientist and devout Roman Catholic.  He discovered that disease is caused by unseen germs and that the fermentation of wine and beer is caused by yeast.  His discoveries had many practical applications for improved public health, but he also applied himself to the investigation of Spontaneous Generation.  During the 1860s his experiments showed that spores of living organisms are carried on dust in the air, thus the organisms found growing on broth do not come from nowhere and will not grow in the absence of dust.  The French Academy of Sciences awarded him a prize for this discovery in 1862.

During the course of the 20th century science has revealed to a greater and greater extent the complexity of even the simplest life, and the difficulty in explaining its origin.  The simplest living organism, a unicellular bacterium, is immensely complex.  As the resolving power of microscopes has advanced, the living cell has revealed itself as a microcosm replete with cell organelles performing the tasks of living with astonishing precision and orderliness.

#1 Origin of Life – Chance, Unknown Law or Design?

The Steps of Creation Part I Chapter 9 – a series of posts taken from the book on the theme of evolution: what it can achieve and what it cannot achieve.

Introduction

The investigation into the origin of life is one of the most speculative areas of science, but it is of the utmost importance to NeoDarwinism.  The NeoDarwinist project does not exist without the proposition that life arose by natural means.  As we will see, there are enormous difficulties in explaining and demonstrating how this could have been.  As scientists enter deeper and deeper into the secrets of life, the gulf between the simplest forms of life and no life manifests itself with greater and greater clarity. Attempts to find a natural explanation for the origin of life have gone on for over half a century now.  Some believe that there will be a break-through, and others believe that the problems are insurmountable.  And there we have it: it is a question of belief.  There is no known law for life to emerge from non-life.

“Was the start of life an accident, or the inevitable outcome of natural laws, or perhaps the deliberate act of a powerful supernatural being?”  (Shapiro 1986, page 30).

Did life evolve by chance as a happy one-off accident on a planet called Earth in an immense universe?  Is the evolution of life inevitable on inhabitable planets due to some unknown law that causes a rise in the complexity and interconnection of organic molecules?  Did God use natural processes to cause life to emerge from matter in the universe?  Did God create life by carefully designing its organic components such that they perform functions of amazing intricacy?  It is all a matter of belief.