Portrait of Sir Hans Krebs (1900-81), German- British biochemist and Nobel Laureate. Krebs trained, like his father, in medicine. During 1932 he discovered the ornithine cycle, in which the liver converts amino acids to nitrogen and urea. The following year he fled from Nazism to Britain. He eventually settled in Sheffield, and it was there that he discovered the Krebs cycle. This describes how the body breaks down glucose into carbon dioxde, water and energy. This is central to energy production in the mitochondria of most cells, and generates energy for whole organisms. For this work he shared the 1953 Nobel Prize with F.Lipmann.