Sir Hans Adolf Krebs was a German-born British biochemist who contributed immensely to the discovery of metabolic cycles such as the Urea Cycle and the Citric Acid Cycle, also known as the Krebs Cycle. Hans was born in Hildesheim, Germany, to Georg Krebs, a surgeon specializing in ear, nose, and throat ailments. He first attended the University of Göttingen to do his medicine before moving to the University of Freiburg and later to the University of Berlin. He completed his M.D. in 1925 at the University of Hamburg and continued his studies in chemistry, to which he devoted his future career and biochemical research.

Krebs established his scientific career when he moved to the Kaiser Wilhelm Institute for Biology in Berlin, where he worked under Otto Warburg. He then went back to clinical work at different hospitals in Germany. His research was significant in the discovery of the urea cycle, a metabolic cycle responsible for synthesizing urea in the liver, and this was the first cycle ever discovered. Nonetheless, Krebs' experience in Germany was not extended because the Nazi regime expelled him from his university post because of his Jewish background. He escaped to Britain in 1933 and continued with his research. In 1937, while at the University of Sheffield, he identified the citric acid cycle, which is essential in aerobic organisms for energy metabolism. He was awarded the Nobel Prize in Physiology or Medicine in 1953.

Krebs later became a professor at the University of Oxford, leading several research studies in cell metabolism. He was knighted in 1958 for his services in science and published several papers until 1967 when he retired. Krebs remained scholarly even after his retirement, participating in more than one hundred scientific papers until he died in 1981 in Oxford.