What branch of chemistry is concerned with the chemistry of living organisms?

The branch of chemistry concerned with the chemistry of living organisms is biochemistry. It examines the molecules and chemical reactions that make life possible, from how cells obtain energy to how genetic information is copied.

Biochemistry focuses on major biological molecules such as proteins, nucleic acids, carbohydrates and lipids. It also studies enzymes, which speed up chemical reactions, and metabolism, the interconnected network of reactions that builds cellular materials and releases usable energy. DNA and RNA are central subjects because they store and help express biological information.

The field developed as chemistry and physiology increasingly overlapped during the 19th century. Anselme Payen's 1833 discovery of diastase, now known as amylase, is sometimes cited as an early milestone. Eduard Buchner's 1897 demonstration that fermentation could occur in cell-free extracts helped establish that biological reactions could be studied chemically outside living cells.

Biochemistry is closely related to molecular biology, but the terms are not identical. Biochemistry emphasizes chemical structures and reactions, while molecular biology often concentrates on how those molecules control cellular information and function.