Hypercycle
A hypercycle is a cyclical sequence of self-reproducing individual cycles. These individual cycles consist of RNA and protein molecules , which depend on each other and cooperate through feedback . The hypercycles described by Manfred Eigen and Ruthild Winkler are seen as an explanation for the prebiotic development of replicative chemical systems. They stand in the transition area between chemical and biological evolution .
In hypercycles , RNA molecules catalyze the formation of such proteins, which in turn catalyze the formation of the RNA molecules. Hypercycles are also subject to evolution: mutations in the base sequence of the RNA lead to molecules with different catalytic properties and thus to different replication rates . Those chemical systems have an evolutionary advantage over others in the competition for the chemical building blocks of the “primordial soup”, which have a high rate of multiplication, i.e. they multiply faster.
Nucleic acid-protein hypercycle
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The circular loops represent the autocatalytic reproduction of the nucleic acids, the red dots the proteins. The nucleic acid N1 synthesizes protein P1, protein P1 catalyzes nucleic acid N2, etc.
Self-reproductive hypercycles of the macromolecules nucleic acid and protein, although still inanimate, have two new abilities that are crucial prerequisites for the development of life:
- The nucleic acids contain a blueprint (the sequence of their nucleic bases ) with the information for their reproduction; they can therefore reproduce through copies.
- The blueprint established by the nucleic bases is biochemically designed in such a way that there is a certain, not too great probability of errors occurring during reproduction and thus further development of the blueprint is possible. So not only is matter passed on, but information for the organization of matter is also “inherited”.
This dissipative autocatalytic process of cyclical self-reproduction takes place with the consumption of energy and more complex molecules such as phosphoric acid , sugar and amino acids ; simpler molecules are released. The process can also be viewed as the coevolution of nucleic acids and proteins, as the first form of a symbiosis : the two “types” of molecules promote each other. This “ phylogenesis ” of molecules enables the development of molecules of higher complexity.
In the hypothetical development of the nucleic acid-protein hypercycles, life is not yet generated, but increasingly complex nucleic acids and the associated proteins over time. A hypercycle amplifies and reproduces itself autocatalytically as a whole when it is closed, i.e. it is fed back into itself: In the picture, the protein P5 again catalyzes nucleic acid N1. A closed hypercycle has a speed advantage in replication. Nucleic acid-protein hypercycles are therefore subject to evolution: hypercycles with a high speed of reproduction have an evolutionary advantage compared to hypercycles with a lower speed, because they "multiply" faster. Their high rate of evolution is also one of the factors that make it understandable that life on earth could develop at all.
Nucleic acid-protein hypercycles already show the properties of living beings: self-reproduction, isolation, transmission of information and metabolism. This theory is described mathematically in the theory of the quasi-species . They are a preliminary stage of evolution and a sub-area of the dissipative emergent processes in nature and society.
More hypercycles
Also, cells , bacteria and other living things are to be regarded as a complex hypercycles because they are composed of many hierarchical build on each other, often feedback processes.
There is even a model of a global dissipative overall system of the terrestrial biosphere by Lynn Margulis and James Lovelock , which was named after the Greek earth goddess Gaia and which works like a complex hypercycle: the model of the Gaia hypothesis . The biosphere is seen as a back-coupled, non-linear system that organizes and regulates itself dynamically and that has so far also coped well with external disturbances.
Its educts are the radiation energy from the sun and the material of the earth, especially that on the earth's surface and in the sea. Its global product is entropy , which it exports into space with its nocturnal radiation. The basis of the "System Gaia" is the incredibly robust and constant ecosystem of bacteria, not only as the basis of evolution and the transformation and stabilization of the oxygen biosphere, but also, for example, in symbioses with higher organisms than intestinal bacteria and in global disposal and recycling the remains of plants and animals.
There is also an alternative model of the biosphere that - in the long run - makes less optimistic predictions than Gaia: Peter Ward's Medea Hypothesis .
See also
literature
- Dieter Braun, Cristof Mast, Friederike Möller: Living non-equilibrium. In: Physics Journal. Volume 12, No. 10, 2013, p. 29
- Manfred Eigen, Ruthild Winkler: The game - natural laws control chance. Piper-Verlag, Munich / Zurich 1976, ISBN 3-492-02151-4
- Manfred Eigen, Peter Schuster: The Hypercycle. A Principle of Natural Self Organization. Springer, Berlin 1979, ISBN 978-3-540-09293-3
- Erich Jantsch: Self-organization of the universe. P. 43
- Ulrich Kull: Evolution. JB Metzler, Biology Study Series Volume 3, p. 34 ISBN 3476200604
Individual evidence
- ↑ M. Eigen, CK Biebricher u. a .: The hypercycle. Coupling of RNA and protein biosynthesis in the infection cycle of an RNA bacteriophage. In: Biochemistry. Volume 30, Number 46, November 1991, ISSN 0006-2960 , pp. 11005-11018, PMID 1932025 (review).
- ↑ Manfred Eigen: Steps to Life. Piper 1987
- ↑ Günter Dedié: The power of the laws of nature - emergence and collective abilities from the elementary particles to human society. 2nd edition, tredition 2015