Основные гипотезы возникновения жизни на Земле
Molecules of life met on clay
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- Life began at deep-sea vents
- Life had a chilly start
- The answer lies in understanding DNA formation
| Molecules of life met on clay
The first molecules of life might have met on clay, according to an idea elaborated by organic chemist Alexander Graham Cairns-Smith at the University of Glasgow in Scotland. These surfaces might not only have concentrated these organic compounds together, but also helped organize them into patterns much like our genes do now. The main role of DNA is to store information on how other molecules should be arranged. Genetic sequences in DNA are essentially instructions on how amino acids should be arranged in proteins. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves. Or maybe life began at the bottom of the sea. Keep going to learn how. Life began at deep-sea vents The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents spewing key hydrogen-rich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems. The next idea is a chilling thought. Read on! Life had a chilly start Ice might have covered the oceans 3 billion years ago, as the sun was about a third less luminous than it is now, scientists say. This layer of ice, possibly hundreds of feet thick, might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, allowing key reactions to happen. [Related: The Ingredients of Life] Understanding life’s origin may involve unravelling the mystery of DNA's formation, as we explain next. The answer lies in understanding DNA formation Nowadays DNA needs proteins in order to form, and proteins require DNA to form, so how could these have formed without each other? The answer may be RNA, which can store information like DNA, serve as an enzyme like proteins, and help create both DNA and proteins. Later DNA and proteins succeeded this "RNA world," because they are more efficient. RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question still remains how RNA got here in the first place. And while some scientists think the molecule could have spontaneously arisen on Earth, others say that was very unlikely to have happened. Other nucleic acids other than RNA have been suggested as well, such as the more esoteric PNA or TNA. A study in 2015 suggests the missing link in this RNA puzzle may have been found. We have two last ideas to throw at you . . . жүктеу/скачать 2,74 Mb. Достарыңызбен бөлісу:
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