On November 22, 1981, biochemist and physician Hans Krebs, co-winner of the 1953 Nobel Prize for Physiology or Medicine for his discoveries of several processes employed by human and other cells to convert nutrients into physical energy, died, at age 81. His best-known discovery is how the body uses oxygen to break down sugars, fats and proteins into energy-rich compounds in a biochemical cascade that today bears his name – the Krebs cycle.
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Hans Adolf Krebs was born in Hildesheim, Germany (near Hanover) on August 25, 1900. His father, Georg Krebs, was an ear, nose and throat surgeon. His mother was the former Alma Davidson, the daughter of a banker. Both of his parents were Jewish, but believers in assimilation. Hans was the middle of their three children.
Six months before his scheduled graduation from the Gymnasium Andreanum, in Hildesheim, in September 1918, Hans was drafted into the Imperial Army. Two months later, after the armistice, he was released from his service, and, having already decided he wanted to follow his father into his otolaryngology practice, entered medical school at the University of Goettingen in mid-semester.
Hans soon transferred to the University of Freiburg, and spent the next few years there and in Munich and Berlin involved in coursework, research and clinical experience. By the time he received his medical degree, in 1925, he recognized that his preference was for research, and that he needed to learn more chemistry.
He was fortunate enough to get a paid position as research assistant to Otto Warburg, a brilliant but demanding biochemist who himself would win a Nobel Prize in 1931 for his study of enzymes.
Nazis' loss, Cambridge's gain
Krebs’ work in Warburg’s lab led him to become interested in study of human metabolism. When his work with the master came to an end in 1930, he found a clinical position in Altona, followed by another one in Freiburg, both of which permitted him to pursue research as well.
By the end of 1932, working with an assistant named Kurt Henseleit, Krebs had figured out the series of reactions within the human cell by which amino acids and ammonia were turned into urea, while at the same time yielding significant amounts of chemical energy. The reactions he identified had the added characteristic of being cyclical, yielding byproducts that were used to begin the processes again, thus providing a constant source of energy.
Despite Krebs’ rising star in the German research world, the rise of the Nazis’ to power, in early 1933, led to his immediate expulsion from his position at Freiburg. Fortunately, he was offered almost immediately jobs at the University of Cambridge, in England, and to Harvard University. He chose the former, and moved to Cambridge in July 1933.
Bemused by the complexity of existence
Cambridge was followed by the University of Sheffield (1935-1954), the University of Oxford (1954-1967), and finally, after mandatory retirement from Oxford, a position at the Radcliffe Hospital in that city. He was awarded the Nobel Prize, together with Fritz Lipmann, in 1953 – Krebs “for his discovery of the citric-acid cycle” and Lipmann “for his discovery of co-enzyme A,” an important facilitator of the process delineated by Krebs.
Krebs continued with his research until nearly the end of his life, and his field of inquiry continued to be the mechanics of metabolism. He also was concerned with a desire to understand the evolutionary logic for the processes he had studied, and was stymied until quite late in his career by the question of why the some of those pathways were as complex as they were. Wouldn’t it have been advantageous, from an evolutionary point of view, for the mechanisms to have been simpler?
A discovery made by an Oxford colleague, organic chemist Jack Baldwin, in 1980, provided the answer Krebs was seeking, and sent him off, at the age of 80, in trying to determine if all metabolic pathways were in fact the most direct and straightforward they could be. It was on this problem that Krebs was working when he died on November 22, 1981, after a brief illness.