Krebs, Sir Hans Adolf (1900-1981), a German biochemist working in England, shared the 1953 Nobel Prize in physiology or medicine. He received the award for his discovery in 1937 of the citric acid cycle in metabolism (see Metabolism ). In this cycle, called the Krebs cycle, tissues use carbohydrates, fat, and protein to produce energy. In 1932, Krebs announced the discovery of how another cyclic process forms the compound urea in the liver. Krebs was born on Aug. 25, 1900, in Hildesheim, Germany. In 1958, Queen Elizabeth II knighted him. He died on Nov. 22, 1981.
