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DNA structure (1D65)^[24]

It was once generally believed that life and its materials had some essential property or substance (often referred to as the "vital principle") distinct from any found in non-living matter, and it was thought that only living beings could produce the molecules of life.^[25] Then, in 1828, Friedrich Wöhler published a paper on the synthesis of urea, proving that organic compounds can be created artificially.^[26] Since then, biochemistry has advanced, especially since the mid-20th century, with the development of new techniques such as chromatography, X-ray diffraction, dual polarisation interferometry, NMR spectroscopy, radioisotopic labeling, electron microscopy, and molecular dynamics simulations. These techniques allowed for the discovery and detailed analysis of many molecules and metabolic pathways of the cell, such as glycolysis and theKrebs cycle (citric acid cycle).
Another significant historic event in biochemistry is the discovery of the gene and its role in the transfer of information in the cell. This part of biochemistry is often called molecular biology.^[27] In the 1950s, James D. Watson, Francis Crick, Rosalind Franklin, and Maurice Wilkins were instrumental in solving DNA structure and suggesting its relationship with genetic transfer of information.^[28] In 1958, George Beadle and Edward Tatum received the Nobel Prize for work in fungi showing that one gene produces one enzyme.^[29] In 1988, Colin Pitchfork was the first person convicted of murder with DNA evidence, which led to growth of forensic science.^[30] More recently, Andrew Z. Fire and Craig C. Mello received the2006 Nobel Prize for discovering the role of RNA interference (RNAi), in the silencing of gene expression.^[31]
Starting materials: the chemical elements of life[edit]

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The main elements that compose the human body are shown from most abundant (by mass) to least abundant.

The four main classes of molecules in biochemistry (often called biomolecules) are carbohydrates, lipids, proteins, and nucleic acids.^[33] Many biological molecules are polymers: in this terminology, monomers are relatively small micromolecules that are linked together to create largemacromolecules known as polymers. When monomers are linked together to synthesize a biological polymer, they undergo a process calleddehydration synthesis. Different macromolecules can assemble in larger complexes, often needed for biological activity.