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2.4 How Life Began Version 1.2 March 2012
2.4: Chemistry and Biochemistry Conclusions (Statement
10) Science has explanations of how life
might have begun. Science currently has
explanations for: ● How the basic building blocks of life formed, such as
nucleic acids and amino acids, following ordinary chemical processes; ● Possible ways how these building blocks over a very long
period became self replicating systems, combining to form RNA then DNA and
proteins; ● Possible ways how these progressed to forming cells; ● How biochemical life processes occur now, such as
photosynthesis, respiration and reproduction; ● How life subsequently changed the atmosphere, the soils and
the seas. …more PROPOSITIONS FOR THE NEXT LEVEL OF DETAIL ARE STILL BEING DEVELOPED. This brief summary will be updated after more work and review against the experts, and over the longer term it can be updated as science learns more, but it will only be replaced by a better story. Simple ‘organic’ molecules, those which contain carbon atoms, occur naturally, even in space, combining with hydrogen, oxygen, nitrogen, phosphorous and other atoms. Over billions of years more complex combinations formed, in the Earth’s water s, near a heat source (such as undersea hydrothermal vents). Some more stable ones which by chance had the right shapes to help similar complex molecules to form would have become more numerous. Some of these would have formed into vesicles, like drops of oil in water, initially very unstable, sometimes simply breaking up to make several smaller vesicles. As millions of years passed and different combinations arose by chance, some would have become closer to the living cells we see today, with chemical pathways transferring atoms and molecules and energy across the cell walls. Other chemical processes made copies of key molecules that allowed more cells to form and allowed broken molecules to be replaced. Initial simple cells (perhaps like the prokaryotes today) somehow absorbed other cell varieties, which are now “organelles” within cells (such as mitochondria and chloroplasts) of eukaryotes. The chemical process called photosynthesis in plant cells, then as now, makes oxygen, which is where the oxygen we humans breath comes from. The process called respiration uses oxygen to make energy available within animals. Many cells made multiple copies of their genes then reproduced by splitting themselves in half so some copies of the genes were in each half. As millions of years passed and different combinations arose by chance, some cells reproduced by joining with another similar cell and mixing their genes, which is the beginning of sexual reproduction. * * * * * * *
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