Sir Hans Adolf Krebs was a physicist and biochemist who is most renowned for his discoveries concerning cellular respiration, a biochemical pathway in cells that enables the production of energy. He discovered two important chemical reactions in the body; the urea cycle and the citric acid cycle.
Krebs was born and raised in Germany, and followed in his father’s footsteps setting up a medical practice which specialised in eye, ear, nose and throat ailments.
He increasingly became more interested in research than treating patients, and started studying respiration. Scientists already realised that respiration in cells occurred in a series of small steps, and each step releases a tiny amount of energy.
In 1932, Krebs discovered the chemical steps by which urea was produced in the liver, a remarkable discovery because it was the first example of the biochemical cycle. The discovery brought him international recognition, and he was invited to work at one of the world’s leading centres of biochemical research, at the University of Cambridge.
A year later, Krebs fled to England when the Nazis took power. As he was Jewish, he been denied academic employment. The Nazis only allowed him to take a few personal possessions, but Krebs did manage to take some of his laboratory equipment so he was able to continue his research even with limited financial resources.
Hans Krebs' classic paper on the Krebs cycle, perhaps the most important development in cell biology in the 20th century, was rejected by Nature. They said it was of insufficient general interest. He went on to win the Nobel prize for that.
In 1937, Krebs published his most famous discovery: the citric acid cycle, also known as the Krebs cycle. The citric acid cycle has been found in a wide variety of organisms, including bacteria.
However, Krebs himself did not know where the Krebs cycle occurred in the cell. Scientists suspected that the reaction occurred in mitochondria, but this was not proven until a decade after Kreb’s discovery.
Krebs worked at the University of Oxford from 1954 to 1967. Along with British biochemist Hans Kornberg, he wrote Energy Transformations in Living Matter in 1957, and also co-authored with Anne Martin Reminiscences and Reflections in 1981. He received a knighthood in 1958, and was awarded the Copley Medal from the Royal Society in 1961.