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What forms “life”? This article summarizes a series of briefs in The Economist that explain life from molecular building blocks up. Beginning at proteins and nucleic acids and ending as “species”, it condenses aspects of organic chemistry and biology into a short survey and glosses over much, but it attempts to draw a big picture for the general reader.
Proteins and Nucleic Acids
Biological molecules are big in comparison to inorganic ones. They can have thousands and sometimes billions of atoms. They have a structure that allows them to be recreated very accurately. Proteins and nucleic acids are two types of large molecules that perform two functions: the former, to catalyze the copying and the latter, to store and transmit information that’s copied. Both of these are polymers, long strings of similar items. Nucleic acids are made from just five different monomers, called nucleotides; proteins from 20 different amino acids.
This design means that many different molecules can be made from the same components of nucleic acids and proteins. Their lengths vary: human DNA molecules range from 17,000 nucleotides to over 100 million! Their order and how the long chains fold upon themselves, determine the shape of the proteins and their function. “The process can create a remarkable number of shapes and…