The Krebs Connection

How is a Nobel Prize winning discovery by Sheffield scientist Sir Hans Krebs linked to the Tour de France?

Who was Sir Hans Krebs?

Sir Hans Krebs, Lecturer in Pharmacology (1935-45) and Professor of Biochemistry (1945-54) at The University of Sheffield won a Nobel Prize in 1953 for the development of the citric acid cycle — also known as the tricarboxylic acid cycle (TCA cycle), or the Krebs Cycle, - which explains how life-giving energy is set free in cells by oxidation of glucose to carbon dioxide and water.

Sir Hans Krebs came to the University of Sheffield as Lecturer in Pharmacology in 1935. He was a German Jewish refugee who had already discovered the ornithine (urea) cycle at Freiburg before being forced to flee the country in 1933.

He found a temporary home in Cambridge before being invited to Sheffield, where he was to stay for 19 years. In 1937, aided by his postgraduate student William Arthur Johnson, he discovered the citric acid cycle (the Krebs cycle) – the chemical reactions during respiration which convert glucose and oxygen into carbon dioxide, water and energy.

Although his work was closely related to pharmacology, Krebs was in essence a research biochemist. In recognition of this, the new Department of Biochemistry was created for him in 1938 and he became Professor in 1945. He received the Nobel Prize for Medicine/Physiology in 1953, was knighted five years later and received an honorary degree (DSc) from the University of Sheffield in 1959.

Sir Hans Krebs

He died in Oxford in 1981 but his name and legacy live on in Sheffield including with the Krebs Institute,  a multidisciplinary research centre with an overall theme of mechanistic biology.

Dr Matt Johnson discusses Krebs, his discovery and its role in endurance sports.

What is the Krebs Cycle and what does it have to do with the Tour de France?

The citric acid cycle — also known as the tricarboxylic acid cycle (TCA cycle), or the Krebs cycle, — is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats and proteins into carbon dioxide and chemical energy in the form of adenosine triphosphate (ATP).

The Krebs Cycle is incredibly important for endurance sport. All athletes need energy for their muscles to contract and this energy is created in the mitochondria which are like the tiny power stations in your cells. Athletes on the Tour de France will have a much higher mitochondrial density than the average person and it is within the mitochondria where the Krebs Cycle is actually housed.

When endurance athletes like cyclists complete for long periods they begin to rely on alternative sources of energy like fats and the breakdown of proteins into amino acids and its the Krebs Cycle that provides the entry point for them to be broken down as energy inside the cell – an incredibly important process for tough endurance events like the Tour de France.

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