Biochemistry is the study of the chemical processes and reactions that take place within living organisms. It can be considered a subdivision of both chemistry and biology, although the skills and techniques used within it place great emphasis on traditional chemistry.
For a very long time, it was thought that living and non-living matter were fundamentally different. Most scientists believed that only living beings could create special biological molecules, from other biological molecules obtained through food. These molecules were thought to be imbued with a “vital force” that made life possible. In 1828, the German chemist Freidrich Wöhler put an end to this by accidentally synthesizing the organic chemical urea — a major component of urine — from inorganic precursors. The field of biochemistry was born.
Since 1828, studies in the field have brought scientists knowledge of the way plants extract energy from the sun (photosynthesis); how animals convert glucose into the energy currency of the body, ATP (glycolysis); why the muscles burn when a person vigorously exercises (the production of lactic acid); how proteins are synthesized in the cell (protein expression); and much more. As living things tend to be the most useful and important arrangements of matter on Earth from many people's perspective, knowledge of their inner workings has useful applications in many areas, including in medicine, agriculture, and molecular biology.
Some molecules studied by biochemists include carbohydrates, proteins, lipids, and nucleic acids. Most of these are organic polymers, meaning they primarily consist simple molecular patterns (monomers) repeated multiple times in a chain, sometimes thousands of times. The primary elements found in organic compounds are carbon, oxygen, hydrogen, nitrogen, calcium, and phosphorous, with trace amounts of chlorine, sulfur, potassium, sodium, magnesium, iron, and a few others.
Many of the molecules in the body, including the carbohydrates and proteins, serve in structural roles. Proteins are manufactured directly based on genetic instructions, and are among the most complex organic molecules. Nucleic acids are the building blocks of genetic instructions (DNA and RNA) found in all forms of life, from humans to viruses. The distinct pattern of nucleic acids found in the nuclei of a species' cells is called its genome. Then there are the lipids, the catch-all term for many non-water-soluble biomolecules. The fat in the body is made of lipids.
Biochemistry is studied by tens of thousands of professionals each day. They seek to understand better how life works and how people can both protect it and use it to make life better.