German-born British biochemist who discovered the tricarboxylic acid, or Krebs, cycle – the series of chemical reactions that are fundamental to the metabolism of living organisms. For this he was awarded the 1953 Nobel Prize for Physiology or Medicine. He was knighted in 1958.
Born in Hildesheim, Lower Saxony, Krebs studied medicine at the universities of Göttingen, Freiburg, and Munich before receiving his MD from Hamburg University in 1925. Thereafter he worked as an assistant in Otto Warburg's department at the Kaiser Wilhelm Institute (1926–30), as an assistant at Hamburg Municipal Hospital, and at Freiburg University. Growing antisemitism forced him to flee Germany in 1933 and he obtained a post at Cambridge University under Sir Frederick Gowland Hopkins, receiving his MA in 1934. The following year he was appointed lecturer in pharmacology at Sheffield University, becoming head of the biochemistry department (1938) and professor of biochemistry (1945) as well as director of the Medical Research Council's cell metabolism unit at Sheffield.
In 1932, at Freiburg, Krebs established the series of chemical reactions by which ammonia, produced by the breakdown of amino acids, is converted to the much less toxic compound, urea, prior to excretion – the urea cycle. In 1937 he went on to unravel the chemical pathway by which food is converted to usable energy. Using pigeon liver and breast muscle, Krebs found that the pyruvic acid resulting from the initial breakdown of carbohydrate (glycolysis) is oxidized to carbon dioxide and water via nine intermediate reactions involving a series of carboxylic acids together with various enzymes and cofactors. The Krebs cycle not only drives the production of the metabolic fuel needed for muscle contraction and other energy-demanding processes but also forms a metabolic crossroads for the synthesis and breakdown of lipids and proteins as well as carbohydrates.
Krebs became a fellow of the Royal Society in 1947 and was appointed Whitley Professor of Biochemistry and fellow of Trinity College, Oxford (1954–67). With Hans Kornberg (1928– ), he wrote Energy Transformations in Living Matter (1957).
Subjects: Science and Mathematics.