Space and time began about 13.7 billion years ago but it consisted almost exclusively of hydrogen until some stars grew sufficiently massive to create the heavier elements in gigantic explosions called supernovae.
The Sun formed about 4.6 billion...
Author's note. You do not need to fully understand this chapter to enjoy the following parts.
The building blocks of life are elegantly simple.
Ribose with five carbon, ten hydrogen and five oxygen atoms, a molecule with a total of only 20 atoms, is part of the backbone of ribonucleic acid (RNA).Four of the carbon atoms (not shown) are at four corners of the pentagram in the diagram. Four other hydrogen atoms are also not shown.
Deoxyribose, which forms the twin backbones of deoxyribonucleic acid (DNA), has one less oxygen atom than ribose.
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Nucleobases. Four of these which, when linked to the deoxyribose molecules that make up deoxyribonucleic acid (DNA), form the genetic code specifying every detail of every living organism.
Adenine (A), cytosine (C), guanine (G) and thymine (T) form the long, helical twin chains of DNA. RNA is formed from Adenine (A), cytosine (C), guanine (G) and uracil (U). Thymine and uracil are identical excepting that thymine includes a methyl group that uracil lacks.
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adenine
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