Where did Glucose come from in a prebiotic world ?
Glucose is a ubiquitous fuel in biology. It is used as an energy source in most organisms, from bacteria to humans, through either aerobic respiration, anaerobic respiration, or fermentation. Sugar phosphates are however constituents of many molecules, such as RNA, DNA, ATP and lipids, which are inevitably connected with the emergence of life. It is the fundamental role of sugar phosphates, and the virtual universality of their few metabolic interconversion sequences, that places their origin to the very early stages in the history of life. Glucose is used by Glycolysis, which is the most universal pathway in all energy metabolism, occurring in almost every living cell. The glycolytic pathway is multifunctional. Thus it provides the cell with energy (ATP)] from glucose catabolism - the process that breaks down molecules into smaller units. Glucose is the human body’s key source of energy. Through glycolysis and later in the reactions of the citric acid cycle and oxidative phosphorylation, glucose is oxidized to eventually form CO2 and water, yielding energy mostly in the form of ATP.
The ultimate origin of Glucose - sugars is a huge problem for those who believe in life from non-life without requiring a creator. In order to provide credible explanations of how life emerged, a crucial question must be answered : Where did Glucose come from in a prebiotic earth ?
The source of glucose and other sugars used in metabolic processes would have to lie in an energy-collecting process. Without some means to create such sugar, limitations of food supply for metabolic processes would make the origin of life probably impossible.
Following are the possible explanations:
Gluconeogenesis is a reverse process to glycolysis, which produces Glucose.
Nonenzymatic reactions that would be precursor mechanisms to glyconeogenesis, leading to the biosynthesis of glucose
Metabolic networks are largely composed of intermediate substrates that are not characterized by long‐time stability, at least when considering geological environments and timescales. In addition, large sugar phosphates are not frequently generated in experiments that address scenarios of primordial carbon fixation.
A paper reports that Fe(II) was broadly available before oxygenation of the early Earth, implying a scenario for the first glycolytic enzymes being simple iron-binding RNA or oligopeptide molecules, which would have possessed the potential of enhancing many reactions now found in central metabolism.
Did you read that carefully ? This is a ridiculous pseudoscientific festival of just so made up fairy tale stories based on wishful thinking. We shall believe that unspecified metal catalysts where somehow ( HOW ??!! ) transformed miraculously and bridged a hudge gap from unspecified chemical reactions into the highly complex specific enzymes, highly regulated by other complex mechanisms, required in these pathways. If such baseless assertions would have been made in ANY other discipline of science, the authors would have been ridiculed. Not so in biochemistry, where any fantastic story is PLAUSIBLE, and is swallowed as serious science.
A paper from Nature magazines reported that Carbonaceous meteorites were a source of sugar-related organic compounds for the early Earth. They claimed :
Sugars, sugar alcohols and sugar acids are vital to all known lifeforms - they are components of nucleic acids (RNA, DNA), cell membranes and also act as energy sources. But there has hitherto been no conclusive evidence for the existence of polyols in meteorites, leaving a gap in our understanding of the origins of biologically important organic compounds on Earth.
Analyses of water extracts indicate that extraterrestrial processes including photolysis and formaldehyde chemistry could account for the observed compounds. We conclude from this that polyols were present on the early Earth and therefore at least available for incorporation into the ®rst forms of life.
Just because something COULD HAVE happened on the early earth, they conclude IT DID happen. The logical fallacy is evident.
1. Natural processes tend to produce gunk with little relevance to life.
2. The amounts of these chemicals were tiny—far too low to contribute to biological processes.
3. Chemical reactions would have somehow to select the useful compounds amongst contaminated gunk.
4. Sugars are very unstable, and easily decompose or react with other chemicals.
5. Living things require homochiral sugars, i.e. with the same ‘handedness’, but these ones would not have been.
6. There is no plausible method of making the sugar ribose join to some of the essential building blocks needed to make DNA or RNA, let alone into RNA or DNA themselves
7. Even DNA or RNA by themselves would not be life, since it’s not enough to just join the bases (‘letters’) together, but the sequence of the letters must consitute meaningful information.
8. Even this letter sequence would be meaningless without elaborate decoding machinery to translate this into amino acid sequences.
Chemisynthesis is employed by organisms that live in the environment around deep-sea volcanic vents, where hot, hydrogen sulfide-rich waters pour out of newly formed ocean crust. Such waters, compared to the colder, sulfide-poor adjacent regions, have an abundant supply of free energy. This term refers to a source of energy that can be utilized readily to do some form of work, such as sustain biological processes, or can be stored in high-energy phosphate bonds. One readily available means to extract energy from the vents is to combine hydrogen sulfide with oxygen to form sulfur dioxide with production of energy. Such a process is possible in an ocean that has free oxygen available, but would not work on the primitive, pre-oxygen-rich Earth. Other biochemical cycles that use sulfur but not oxygen are conducted by some prokaryotic organisms, but these capture much less energy than the oxygendriven cycles. As with fermentation, chemisynthesis without free oxygen was the hallmark of a rather sluggish primitive biota.
There would have had to exist a cell membrane, dividing the outside from the inside of the proto-cell, to protect the chemical reactions, and complex gates regulating the compound entrance into the cell. That is another serious problem for origin of life research:
even in the simplest cells, the membrane is a biological device of a staggering complexity that carries diverse protein complexes mediating energy-dependent – and tightly regulated - import and export of metabolites and polymers Remarkably, even the author of the book: Agents Under Fire: Materialism and the Rationality of Science, pgs. 104-105 (Rowman & Littlefield, 2004). HT: ENV. asks the readers:
Hence a chicken and egg paradox: a lipid membrane would be useless without membrane proteins but how could membrane proteins have evolved in the absence of functional membranes?
The book Origins of Life on the Earth and in the Cosmos tries to solve the ridde as follows :
Membrane-enclosed cells came into being some time after the first ribozymes and definitely before the advent of translation systems. It is highly likely that these primitive living systems were sequestered in some way, possibly by adhering to clay surfaces. It is also likely that the first fatty acids used to make cellular membranes were made under conditions that would have been too harsh to share with living systems that are far more delicate. In view of this we must ask how the first membranes made contact with the early membrane- free living systems. How could life exist without membranes ?
Then we must consider how the early living systems became enclosed by these membranes and how the membranes of these most primitive cells evolved. True. Big questions, isnt it?
The encapsulation of the living systems into the liposomes was probably a simple process that required no more than one or two dry–wet cycles.
The pseudo-scientific just so stories are remarkable, aren’t they ?! The conclusion is that naturalistic explanations do not suffice to answer the relevant question in a satisfying manner, where Glucose came from, adding to all other unbridgeable problems of origin of life research, and thus giving proponents of intelligent design good reasons to infer intelligent design as the better explanation.