Content of essay: “Origin of Life, Molecular Biology, Natural & Human Evolution”:

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Introduction                                            1

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Within individual solar systems, great proximity of planets to their central sun would result in excessive surface heating – with life basically restricted to the very narrow band between 0 and 50^oC surface temperature on planets – for the availability of liquid water and a heat level below destructiveness for large organic molecules (except for extremophile bacteria).A large distance of planets from the central sun would not provide enough heat from this energy source.Depending on the size and age of a star – and its consequent heat-radiating intensity – the habitable zone for its planets would be closer to or farther away from the central star, possibly shifting with the age and radiation of the star.The early Earth demonstrates that atmospheric greenhouse effects allow for the extension of the habitable zone to an area of lower heat reception.This allowed Earth to become habitable at an early time when the Sun had only 70% of its present luminosity.The habitable zone of our solar system, including atmospheric influences, begins beyond Mercury and includes the region from Venus by way of Earth to Mars.Beyond that area, there are not enough heavy elements and an excess of water content (beyond the Asteroid Belt).The outer planets are too cold (distance from Sun), largely gaseous, and, therefore, not considered habitable for life as we know it – except possibly some of their moons that may be kept warm through extreme tidal deformation.In sum, our Earth is in a very habitable zone of the universe, being about 60% of our galaxy’s radius away from its center and, within our solar system, about one hundred times the diameter of our specific sun away from it.

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The assessment whether “habitable zones” are fairly plentiful in the universe and, consequently, whether we humans are a highly unusual phenomenon in the universe, or whether much other intelligent life can be expected in the universe, is a subjective one.Depending upon the individual scientist and the general trend in the sciences at any one time, the glass is either half full or half empty.In times past, plenty of other intelligent life had been expected in the universe.The SETI project [3] was started to discover and communicate with that supposed life.Then, a more critical view arrived and publications [4] pointed out how unlikely any other higher forms of life – specifically, intelligent life – in the universe would be (but not denying the possibility for extensive bacterial life).Lately, the discovery of “extremophile” bacteria deep under ice, at very hot deep-sea vents, or deep within rocks, has opened a view allowing for larger “habitable zones” and, therefore, greater probabilities.But the expected, randomly repetitive large catastrophes remained as the limiting factor, possibly not allowing enough time for the slow development of higher forms of life.But do we really know whether higher evolution must always be slow?

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On the other hand, the recognition of the great resilience of Earth’s atmosphere and the resurgence of ever higher forms of life after each of the past catastrophes should allow for the acceptance of higher comet or meteor risks in the environment and, consequently, larger habitable zones or higher probabilities for advanced forms of life in the universe to develop in the available time.The fact that life on Earth easily survived many passages through the galaxy’s spiral arms and the many reversals in the magnetic field, with consequent higher radiation levels during transition times, should allow for more radiation risks.

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The assumption that higher forms of life have required billions of years to develop on Earth should be put in perspective with the arrival of large quantities of oxygen only some 600 million years ago.This oxygen, consequently, led to the oxidizing of biomaterials as a source of energy and, therefore, required mobility, then leading to nerves and, finally, the brain as the main characteristic of what we call “higher” form of life.

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Life’s development in the last 600 million years was quite rapid, especially during the last 65 million years, after the demise of the dinosaurs.Why could another Earth-like planet in the universe not have shown even faster mammal development?It could have occurred, for example, in lieu of dinosaur development after an earlier catastrophe, hundreds of millions of years earlier in evolution than on Earth.

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In sum, this author assumes a somewhat more temperate position, seeing the very special character of Earth as a harbinger of life in the vastness of the universe, but also seeing the probability for other Earth-like planets in other solar systems and in other galaxies to harbor higher forms of life – with enough shielding against radiation and impacts and with atmospheres with enough resilience, like our own, to overcome catastrophes.This would allow for considerably more intelligent life in the universe than has recently been assumed – specifically in consideration of the very large number of existing galaxies (several billions) and the very large number of solar systems within them (several billions in each of them).

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After all, the product of an exceptionally large number and a small probability still allows for the result to be anything, but possibly also a large number.

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1.2.The Origin of Life

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Living beings are composed of molecules.Certain molecules are called “organic” by scientists, because they were found to appear mainly in combination with, or as products of, processes of living organisms.Later, it was found that some of these organic molecules – they should be called “proto-organic” – existed before life arose on Earth and were the precursors of life.The designation “organic” is misleading.Those molecules – mainly complex compositions of carbon, hydrogen, nitrogen, and oxygen – often containing the famous Kekule-discovered “benzene” hexagonal ring of six carbon atoms – did not originate in the universe in connection with any organic life.Later, however, as life arose, these molecules actually did occur in life processes and became the dominant form of molecules in living beings – hence their group designation as “organic” molecules.

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The question arises why carbon became the key atom in all organic molecules and, consequently, all living organisms – though combined with hydrogen, nitrogen, oxygen, phosphorus, and many spurious materials.Atoms consist of a nucleus composed of positively charged protons and neutrons.They attract negatively charged electrons in a number equal to the protons.The electrons can be visualized as circling the atomic nucleus on a sphere or “shell”.But when more than two electrons are needed for the nucleus, the first shell is full and the extra electrons circle on an additional shell.More electrons are added for heavier nuclei, until, at eight electrons, that second shell is full and another one has to be started – and so on.Electrons can be shared with other atoms, thereby establishing bonds with those other atoms.Two hydrogen atoms, with only one electron each, can establish bonds with an oxygen nucleus requiring two electrons to complete its second shell – thereby forming H₂O, water.Carbon has four electrons in its second shell that could hold eight and, thereby, can establish four bonds in all directions with all kinds of other atoms (nitrogen, the next most important atom in organic chemistry, can have only three bonds and oxygen only two).Those electrons, being of an inner shell, are very stable.This makes carbon a versatile and strong building block for complex structures or chains.In other words, it is the regularity of the electron shell structure of atoms that led to the combinatorial bonding of atoms and that let carbon become the key element of organic composition and consequent natural evolution.

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As described above, simple “organic” but not “living” molecules – such as methane and some amino acids [5] – had already been constructed in cosmic space from the ejecta of collapsed stars by means of ultraviolet light and radioactivity in the universe and were floating around in space before Earth was formed.Consequently, when the origin of Earth took place as it “accreted” (coagulated) in its band of gas and dust around the Sun, such proto-organic molecules became part of Earth and may have survived this forming process, at least at high altitudes of the atmosphere and, less likely so, in some niches of the surface crust, possibly at some depth.On the other hand, Earth reached extremely high temperatures upon accretion, early formation, and under early comet impact and may have become sterilized thereby.

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A different theory concerning the origin of life on Earth appears more promising.During the violent time of Earth’s formation and thereafter, asteroids and comets consisting of ice impacted Earth [6].Four significant factors came together in these comets: dust particles, an icy surface on those particles (or dust on icy surfaces), inclusions of proto-organic molecules in those icy surfaces as available in space, and ultraviolet light.The dust particles that accreted to form the comets consisted of mineral or metallic material.“Cosmic” ice [7] had formed in outer space on these dust particles (or dust particles had accumulated on the ice) and contained already complex organic molecules as available in space – as one knows from the recent investigation of comets.The combination of a catalytic effect of the mineral or metallic surfaces of the dust particles – with the energy provided by ultraviolet radiation as available in space and the effect of the ice to hold the proto-organic material, to give it yet some limited mobility – facilitated the formation of more complex molecules, especially since cosmic ice goes through transformations into different states (amorphous, cubic, hexagonal, and liquid).

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Four resulting organic formations of dust in or on cosmic ice were detected and are of special significance: nitrile, chinon (so named in the related paper, commonly called quinone), adenine, and formaldehyde.

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-Nitriles (for example, Propionitrile[[should this be cap?]] CH₃CH₂CN) consists [[?]] of carbon, hydrogen, and nitrogen atoms.When immersed in water, as when cosmic ice temporarily melts under the influence of radiation or when it hits an ocean on Earth, it is transformed into a lipid acid.Certain lipids (for example, phospholipids and other amphipathetic lipids) can spontaneously form “micelles”. Micelles are hollow spheres or bubbles organized in a double layer of fatty acids, like cell membranes.They permit “protected” chemical evolution in their inner space.

-Quinone can be formed in comets or cosmic ice from the already existent methane, ammoniac, and carbon dioxide.Quinone has certain chemical similarities to chlorophyll [8].On the one hand, it can transform absorbed radiation into chemically stored energy.On the other hand, it protects other proto-organic molecules from the destructive radiation that exists in space and existed on early Earth even before Earth’s final atmosphere was formed.

-Adenine is formed from carbon, hydrogen, and nitrogen atoms.Not only is it one of the nucleo-bases that are the key elements of RNA and DNA as carriers of genetic information, it is also a precursor of adenosine tri-phosphate (ATP) which plays a key role as energy carrier in cellular dynamics.

-Formaldehyde (H₂CO) is the forerunner of ribose or desoxyribose, the sugar backbone of RNA and DNA, both formed out of a polymerization of 5 formaldehyde molecules.

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Some icy comets, as also some rocky comets, do not fully vaporize upon entry into Earth’s atmosphere.Icy comets that do not fully vaporize have the additional advantage of keeping their inner temperatures moderate, thereby allowing the complex proto-organic substances to survive.

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It is known that some of the cosmic proto-organic molecules lead immediately to more complex molecules as they enter the water of Earth’s oceans.

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Calculations indicate that any comet that hit Earth may have deposited 10²⁴dust particles into the early oceans!

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A more detailed discussion would indicate the specific significance of ultraviolet radiation for the promotion of chemical reactions leading to more complex molecules (or the maintaining of a balance between “right-handed” and “left-handed sugars” in the evolution-feeding original organic soup on Earth – or the contribution of ultraviolet radiation to RNA formation).

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In sum, the icy comets may have been the source not only of water for Earth but also of the organic evolution on Earth and the origin of life.This may explain why life originated so quickly, within only 50 million years after Earth had cooled and stabilized.

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Organic molecules found a favorable environment in the early atmosphere and oceans, as well as deep underground, shielded from the effects of the numerous meteor impacts, radiation, and the intense volcanism of the early Earth.

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A famous experiment by scientists shows that additional quantities and types of “organic” material could appear naturally in this environment when lightning hit waters rich in basic proto-organic molecules.More likely, such formations occurred when early organic molecules accumulated on clay or pyrite surfaces or at underwater volcanic vents (“hot-spots”) rich in iron and sulfur efflux [9].Clay and pyrite surfaces are electrostatically attractive to such proto-organic molecules.In environments rich in such molecules, these can form a dense layer on the surfaces of those clays in shallow ponds or pyrites at deep-sea volcanic wells, keeping the individual basic molecules somewhat immobile in close proximity to each other.

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This immobility, however, is not total stillness, since elevated temperature indicates a corresponding amount of “Brownian” movement appearing as a constant “wiggle” of all atoms or molecules within whatever space is available – resulting in corresponding collisions between adjacent molecules.Furthermore, radiation will cause further collisions and will partially impact the electron layers of the molecules – possibly damaging some electron “shells” and dissolving some bonds, but also possibly rendering them receptive to linkage with neighboring other molecules.Actual linkage, then, is a matter of probability and the right temperature, one high enough to permit forceful Brownian and electron-based interaction between molecules, but not too high to immediately destroy newly formed molecules again.

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Considering the “astronomical” number of interacting molecules on all the potentially suitable clay or pyrite surfaces of Earth and the millions of years until DNA appeared on Earth as it cooled down, it is not surprising that critical conditions were reached at one point where RNA or DNA fortuitously formed and remained stable on a clay surface.In a shallow pond – or, more likely, at an underwater hot-spot or “vent” – RNA could have formed first, subsequently forming DNA.

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Anthony Mellersh – in his Origins of Life and Evolution of the Biosphere (23, 261-274), 1993, indicates that an RNA strand adheres to a solid surface in an undulated way.Each of the folds of this undulation happens to be just three RNA bases long, permitting the fitting of certain amino acids into those folds.Could this have been the original process of one being formed from the other, amino acids from RNA or RNA from amino acids – with the rule that three RNA bases are needed for the definition of each amino acid upon translation – thereby being established?Inversely, could the aboriginal amino acids have formed minute bits of RNA on their surface that, when attached next to each other on a clay surface, formed these longer undulating chains and, hence, RNA?Then, only 100 genes on DNA/RNA were necessary to form primitive living organisms [10].

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Luke Lehman (at Scripps, in La Jolla, 2004) demonstrated that extraterrestrial amino acids reaching volcanic underwater vents could combine with carbonylsulfide gases to form peptide chains, the beginning of proteins.

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The present status of science indicates that RNA was the first molecule that was self-replicating, utilized resources from its environment and was leading to evolution, therefore called a “living” molecule.But, while all precursor organic molecules could be synthetically produced by now, it was not yet possible to simulate the natural starting conditions sufficiently to produce RNA synthetically and prove any of the theories of its origin.

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RNA is a very complex molecule – with a complex composition and structure, not flat as shown in chemical formulas on paper, but with a complex, three-dimensional shape.RNA is used by nature to produce amino acids, the building blocks of proteins.Amino acids did occur in outer space and, as indicated, were present on the early Earth or were transported there at a later time.Most, if not all, chemical processes can work in both directions.Consequently, could natural, aboriginal amino acids, some early nucleo-base, and cosmic formaldehyde have led to the formation of the first pieces of RNA?As pointed out in a later chapter, the translation of RNA into amino acids is not simple and commonly utilizes some facilitating proteins.Did some primitive proteins and nucleotides facilitate the back-translation of amino acids into RNA pieces?This may be the bottleneck for synthetic replication of RNA generation and may be providing for the uniqueness of its appearance in the first place.

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One must assume that synthetic production of RNA should be possible in the future through ingenuity or fortuitous circumstances. This leads to the thought of “creating” a new, man-made start of natural evolution based on a variant of RNA.Such evolution could be controlled, in laboratories.But what if some of that new RNA escapes or is exposed to a natural environment somewhere on Earth?What would or could evolve from it over time?Possibly less than science fiction expects – since most niches for survival are filled.But the phenomenon of invasive species taking over new territories tells another story – and so does the precaution of NASA not to expose other celestial bodies with our organisms or Earth to possible organisms from other celestial bodies.

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In any event, it appears as a miracle and singularity of Creation that only RNA appeared, only once, about 3.9 billion years ago as a self-replicating molecule leading to evolution – and, consequently, as the source of life.There is evidence that RNA is self-replicating and can also synthesize DNA (see, for example, the work done by Walter Gilbert, Sidney Altman).DNA is a much more stable molecule, capable of forming long and stable chains by linking multiple molecules like segments of a string together (by means of phosphorus linkage atoms).DNA can reproduce new RNA.

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For these reasons, DNA may have prevailed at that early time over any other possible self-replicating molecules – possibly in the competition for scarce resources – for example, phosphorus – or in competing for favorable territories – for example, the areas with just the right temperature and availability of chemical compounds, as well as sufficiently undisturbed to allow nature to experiment with the formation of those molecules over some period of time.Some scientists believe that it may have taken 10 million years to produce DNA.But, as said, it has not been possible so farto synthetically reproduce any such “living” molecules.

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It is equally difficult to understand why no other self-replicating and evolving molecule, different from RNA or DNA and their derivatives, has ever appeared subsequently in the course of the last 3.9 billion years.Theoretically, other forms of life along the lines of DNA should have become viable, even though propagating less efficiently than the one that prevailed.So many later microbes, plants, and animals have found niches to avoid predators and evolve – but no other “living” molecule ever found a niche in which to appear and start a different, surviving strain of life from that which we know and are made of.This must be counted among the mysterious singularities in evolution, as will be pointed out in a later chapter of this essay [11].

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A much discussed scientific theory indicates that RNA or DNA may have arrived within a meteorite, possibly from Mars, from where many large meteors arrive all the time and many more arrived during the early phase of our solar system [12].This would not solve the problem of the origin of life – it would just antedate and relocate the problem.The same can be said about the “Panspermia” theory, indicating that RNA or DNA may have arrived from outer space beyond our solar system and may be found in many areas of outer space [13].

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There is a new conjecture indicating that the formation and multiplication of DNA were specifically favored on the early Earth by the existence of the Moon [14].At that early time, the Moon was much closer to Earth, as described earlier.Consequently, the tidal waves were enormously larger, washing over wider areas and then leaving them to dry out again.This left more salt in the tidal areas.It is known that the double-stranded DNA helix tends to break up in one condition, only to form a new double helix in the other condition thereafter.Consequently, under the most favorable circumstances, there could have been a doubling of DNA with each tidal cycle, quickly leading to dominance.The problem consists in the fact that this assumes the existence of the Moon close to Earth at the time of the origin of DNA, some almost 4 billion years ago.As indicated above, in the chapter on the origin of the Moon, there are some serious problems with this assumption.

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After all, it appears as if the availability of precursor organic compounds for life’s formation as evolved in cosmic space and deposited on icy comets, then their swift variation or expansion in the early oceans, as described above, may have been the prime candidate for the explanation of the RNA-based origin of life on Earth – and, possibly, in a similar way on other celestial bodies.

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What we describe as life is a self-organizing system of complex molecules – taking on a life and evolution of its own in accordance to its own rules.This is another example of the “Combinatorial Principle,” but also of the “Basic Principle of Evolution”, as explained in Chapter 1.1.5, indicating that the universe evolves as possible at any one time or place in accordance with the then and there given starting and boundary conditions – with evolution being driven by probabilistic or random variations, and finding viability in accordance with opportunity.

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If the origin of a “living” molecule, RNA, was a highly unusual event and occurred only once on Earth, can one say that all natural life on Earth descended from that one single molecule?

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2.Molecular Biology

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2.1.DNA, RNA, Ribosomes, Enzymes, Proteins, Lipids, Carbohydrates, ATP

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In considering the further evolution of life from its mysterious beginning about 4 billion years ago [15], one has to look at the most important organic compounds allowing cells or organisms to live and evolve, described by their scientific designations as nucleic acids, nucleotides, codons, ribosomes, enzymes, amino acids, proteins, lipids, carbohydrates, and adenosine triphosphate, or “ATP”, for short.

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Both RNA and DNA are called “nucleic acids” (DNA = deoxyribonucleic acid and RNA = ribonucleic acid).A preceding chapter presented a discussion on why RNA is assumed to be the source of life on Earth.But RNA itself is not very stable, and any strands of it easily break up into smaller pieces.RNA, however, is thought to have been capable of forming DNA – a much more stable molecule, allowing the formation of very long strands with superb multiplication capability.Thus, DNA is the molecule that became the repository, or archive, of our genetic foundation.RNA remained as the linkage between DNA and amino acids – by creating the amino acid strings that form proteins.

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DNA is formed by two almost identical, twisted strings constituting the famous “double helix”.The individual segments of the DNA strands, the so-called nucleotides described below, consist of sugar molecules with attached “nitrogenous bases”.Each nucleotide along the nucleic acid string is linked to the next one by a “phosphate group”, a single oxidized phosphorus atom.The phosphorus links may allow – with all the necessary stability of those DNA molecules – the introduction of minor variations in the DNA strands under special external influences (chemical- or radiation-related).Such variations can lead to the mutations necessary for evolution, which in turn lead to different or higher forms of life at an acceptable rate.The variations must be slow enough to allow for the development of large colonies of viable living beings.On the other hand, the variations must be fast enough to allow for evolution to use opportunities and avoid risks connected with climatic changes, ecological changes, and the limited lifetime of our Sun and Earth – ultimately to reach the development of higher civilizations in the time between major catastrophes, as described in a later chapter.

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The length of DNA may be only a few hundreds or thousands of nucleotides in simple organisms, but it reaches almost 3 billion of such nucleotide segments in humans.Such a long strand (about 2 meters long, if fully extended) is not left loose in the cell.It is set in a very tight spiral, then, in eukaryotic cells, wound around very small cores (nucleosome particles consisting of four histone proteins) produced in the cell, with just 1.8 windings or 140 base pairs of DNA per core (this DNA section then being called a nucleosome).The nucleosomes are separated by 20 to 100 base pairs of DNA and the whole spiral is then once more formed into a super-spiral.It is intriguing to notice that the spiraling is done in such a fashion as to leave important “addresses” (regulatory elements of the genetic helix) for later transcription accessible on the outside. The still very long spiral of a spiral can then be coiled and formed, upon fertilization or cell division, into some larger species-specific patterns, the so-called chromosomes, including the famous X-shaped and Y-shaped chromosomes of humans.

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Along either of the two helix-intertwined DNA strands, the sugar molecule of each nucleotide is provided with a small protrusion – a “nitrogenous base” in chemical language – consisting of one or two hexagonal or pentagonal rings of carbon and nitrogen atoms with outward-reaching, additionally attached nitrogen or hydrogen atoms.These protruding molecules are connected to the corresponding (and protruding) molecules on the other one of the two twisted DNA strands.The connection is made by two or three hydrogen atoms as bonds at the end of those connecting protrusions, depending on how they are formed (their chemical nature).

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An individual subunit of DNA, the combination of a sugar molecule with its nitrogenous base, is called a “nucleotide”.There are only four different kinds of nucleotides, according to the only four types of attached nitrogenous bases they may possess (called A, C, G, and T or, within RNA, U).When linking one strand with the other along DNA, only certain linkages of bases (or letters, as indicated) from one strand to the other are possible due to the very different configurations of the ends of those bases that have to meet and link between the two strands of DNA – and also to complement each other in their different sizes, thereby keeping the double DNA helix at relatively constant width.

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Subgroups of three adjacent nucleotides along a DNA string are called a “codon”, because it always takes one such codon group of three nucleotides to let the subsequent messenger-RNA produce one specific amino acid as a building block of proteins.The type of amino acid that results is determined by the types and sequence of bases in the codon being expressed.The sequence of codons on DNA results in a corresponding sequence on the messenger RNA and, consequently, in a specific sequence of amino acids in the outgoing string of those amino acids, which is then called a protein.

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A significant string of many codons, resulting in the expression of a protein, is called a “gene”.So far, about 20,000 human genes have been identified and 5,000 more are expected to be identified in the future, for a total of possibly even less than 25,000 human genes.This is just about the number of genes some fishes have and just 25% more than the number of genes for some worms.The difference comes from the capability of the human genome for gene splicing and control.Thereby, the same number of genes can express a vastly larger number of proteins, theoretically in the trillions [16], which is a much larger number than that of some plants and other organisms with larger number of genes but which are not capable of splicing.Additional differences may come from variations in gene coiling (or condensations, compressions) in the chromosomes, providing or inhibiting gene expression (see the new field of epigenetics discussed below).

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RNA is similar to DNA, but consists of only one strand of somewhat different nucleotides.The nucleotide designated by the letter “T” in DNA is replaced by the nucleotide designated by the letter “U” in RNA.Three types of RNA are produced through transcription of DNA.Messenger RNA, the mRNA, is the agent in the creation of amino acids and their chain-like assembly into protein molecules, the main actors of life in the cells.Some amino acids do appear naturally in cosmic space out of the material available from earlier star explosions, transformed by the radiation permeating space.But most of the specific amino acids needed in organisms must be produced by those organisms themselves, beginning with the material that is available in their seed or egg cell.This is accomplished by mRNA based on the code found on DNA.

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Another kind of RNA transcribed from DNA is called “rRNA”.Its transcription from DNA is facilitated by specific molecules called RNA-polymerases.The “rRNA” strings form “ribosomes”.They consist of a combination of several “rRNA” molecules and an additional accumulation of specific protein molecules.Ribosomes are large molecules that facilitate the transcription of mRNA into amino acid sequences, the new proteins.

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Additionally, there is “tRNA”, the “transport RNA”.Its function in transcription is explained later.

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Enzymes:“Enzymes” is the name of the group of proteins that act as catalysts – for example, the above-mentioned RNA polymerase (there are three types of those), facilitating transcription of DNA into RNA.

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Amino acids: The core cluster of an amino acid consists of a nitrogen atom with two or three attached hydrogen atoms (an “amino group”) that is connected to a carbon atom with two attached oxygen atoms (a “carboxyl group”) by way of an intermediate carbon atom.Attached to this core cluster is one of 20 possible chains that define the specific type of the 20 naturally existing amino acids, all designated by a letter (in four groups, containing either D, E, K, R, H, or S, T, Q, N, Y, or A, V, L, I, M, F, W, or G, C, P) [17].These chains consist of as few as one hydrogen atom (in Glycine, designated by the letter “G”) to a chain of six links (in Arginine, designated by the letter “R”), or a combination of a pentagonal plus a hexagonal arrangement of carbon and hydrogen atoms (in Tryptophan, designated by the letter W), and more [18].

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Proteins, also called polypeptides:Proteins consist of chains of amino acids – with the core groups of the different amino acids being linked and their side chains remaining outside.The specific sequence of amino acid types being produced by mRNA transcription is indicated by the sequence of codons on the genome of the DNA that is being transcribed via that mRNA, as described before.The proteins do all the work in any living unit [19] – from the smallest proteins forming “picornaviruses” to the largest knots of proteins in the cells of the human body.

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Protein strings can be up to many hundreds or even thousands of amino acids long.

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Most proteins, specifically the larger ones, do not stay in an extended state but, after being formed, quickly fold into complex shapes. Each type of protein assumes a specific shape.These shapes are composed of spirals (?-helices), bands (?-sheets) and some loose ends, all lumped together in a specific way.The total form may be quite compact, but may also include certain niches where actually most of the protein’s action on, or sensitivity to, its environment takes place.

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There may be 10,000 different types of proteins in a human cell at any one time (up to 50% of its mass) and possibly many hundreds of thousand different types in the human body at different times. 

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Lipids are a diverse group of molecules including fats used by the body for energy storage and lipid bilayers used in the cell as membranes.Lipid bilayers can naturally form spherical arrangements (bubbles) – so-called “liposomes” – providing excellent protection for the inside space within those bubbles.

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The first lipid bubbles may have become available from the nitriles arriving on Earth with icy comets.But, once DNA and the secondary proteins were able to form lipids, it was only a matter of time until this capability led to ongoing production of protective bubbles around the DNA and its associated protein factory – an arrangement we now call “cells”.

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Lipid acids, more commonly now called fatty acids, are chains of, typically, 14 to 20 carbon atoms, each with two attached hydrogen atoms.Their high carbon content explains their energy content when used in the form of fats as nourishment.Fats are three lipid acid chains connected at their end by a combination of a few carbon, hydrogen, and oxygen atoms.Lipid bilayers are double sheets of small interconnected molecules, each having two lipid acid chains attached, but all directed toward the intermediate space between two sheets forming the bilayer.

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Carbohydrates:Carbohydrates include the various forms of sugars and larger molecules composed of sugars.The simple sugars (fructose and glucose) contain short chains of carbon atoms, with attached hydrogen atoms to one side and oxygen-hydrogen atom combinations, on the other, as well as more complex configurations of atoms at the end of the chain.These end-configurations determine the difference between the various sugars.Some sugars can form three-dimensional hexagonal rings out of their chains.Carbohydrates provide an easily accessible energy supply to the body – by way of oxidation in the mitochondria – providing heat and forming ATP – the latter transferring energy to wherever it attaches itself to.

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Glucose, the main energy source for the body, is formed in the liver from various food materials absorbed by the intestines and can be stored in modest amounts in the muscles (in the form of glycogen).Plants store their energy surplus in a multi-molecular form of sugar called “starch” (e.g.