Biochemistry, study of the substances occurring in living organisms and the reactions in which they are involved. It is a science on the border between biology and organic chemistry. The main constituents of living matter are water, carbohydrates, lipids, and proteins. The total chemical activity of the organism is known as its metabolism. Landmarks in biochemistry include the synthesis of urea by Friedrich Wöhler (1828), the pioneering research of Von Liebig, Pasteur, and Bernard, and, more recently, the elucidation of the structure of DNA by James Watson and Francis Crick (1953).