University of Zagreb. Faculty of Science. Department of Biology.
Abstract
Predmet istraživanja porijekla života jest rasvjetljivanje puta koji je od jednostavnih kemijskih spojeva doveo do nastanka LUCA (last universal common ancestor) - zajedničkog pretka svih organizama. Zemlja je nastala prije oko 4.6 milijardi godina, a prvi dokazi života sežu 3.86 godina u prošlost, kada su na Zemlji još uvijek vladali reducirajući uvjeti uz obilje amonijaka, metana, dušika, ugljikova dioksida, vodika i vodene pare. Budući nije bilo kisika, nedostajao je i ozonski sloj, te je UV-zračenje u cijelom svom intenzitetu dolazilo do površine zemlje. Postoje mnoge teorije gdje je u uvjetima koje je pružala mlada Zemlja život mogao nastati: od ideja da je život došao iz svemira, preko vrućih izvora na površini zemlje do dubokomorskih hidrotermalnih izvora. Svaka od teorija ima svoj odgovor na pitanje je li prvo evoluirao metabolizam, u kojem se kasnije razvila molekula koja je mogla prenositi gensku informaciju, ili je prvo nastala molekula prenositelj genske informacije uz koju je kasnije evoluirao metabolizam. No, većina se slaže da je primarnu uloga prijenosa genske informacije vjerojatno imala RNA koja, za razliku od stabilnije DNA koja danas posjeduje tu ulogu, osim mogućnosti pohrane informacije u obliku slijeda nukleotida posjeduje i katalitičku aktivnost. Također, većina se i slaže da su za nastanak života bili izrazito bitni metalosumporni spojevi koji su imali katalitičku aktivnost, a očuvani su i danas kao dio, biokemijski vrlo bitnih, metaloproteina. Još uvijek ne znamo konačan odgovor na pitanje: „Kako je nastao život?“, ali svako novo otkriće je komadić slagalice koja daje odgovor na to pitanje.The object of origin of life research is to elucitade the pathway leading from simple chemical compounds rise to the LUCA (last universal common ancestor) - the common ancestor of all organisms. Earth was formed about 4.6 billion years ago, and the first evidence of life dates 3.86 years in the past, when the Earth was still characterized by reducing conditions with an abundance of ammonia, methane, nitrogen, carbon dioxide, hydrogen and water vapor. Since there was no oxygen, the ozone layer was also missing, and UV-radiation reached the surface of Earth in whole of its intensity. There are many theories where, in the conditions that early Earth offered, life might have originated: from the idea that life came from outer space, via the hot springs on the Earth's surface to the deep-sea hydrothermal vents. Each theory has its own answer to the question whether the metabolism is the one that evolved first and later developed a molecule that was able to carry and store genetic information, or the the molecule that carried genetic information first evolved around which later evolved metabolism. However, most agree that RNA had the primary role of storing replicable genetic information which, in contrast to the more stable DNA which now plays this role, in addition to capacity to store genetic information in the form of a sequence of nucleotides also possesses catalytic activity. As well, most agree that metallosulfuric compounds, that showed a catalytic activity and are preserved today as part of biochemically important metalloproteins were extremely important for the emergence of life. We are still not able to doubtlessly answer the question "How did life originate?", but each new discovery is part of the puzzle that gives us the answer
