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The Story Behind Peter Mitchell's Chemiosmotic Theory

Peter Mitchell

28 Jun 2016

Energy that is provided through food, light, or a myriad of other sources can be converted into ATP, or adenosine triphosphate, by living organisms. ATP synthesis is associated with respiratory and photosynthetic processes catalyzed through complex redox enzymes embedded in lipid membranes. Today, this is accepted knowledge. However, when Peter Mitchell first postulated a mechanism for this in 1961, through his chemiosmotic theory, it was immediately met with hostility. Professor Peter Rich of University College London recounted the history of Mitchell’s chemiosmotic theory through an engaging lecture at New York University London on 9 March 2016 demonstrating how a rejected hypothesis became an accepted theory.

Professor Rich took an interesting approach in discussing Mitchell’s theory. He talked about the different scientists whose work had influenced Mitchell’s ideas. These scientists included Robin Hill with his discovery of the famous Hill reaction and advances in the study of photosynthesis, Han Krebs’s work on the citric acid cycle, and David Keilin with his concept of the cytochrome respiratory chain. All of this earlier work laid the foundations for energy production in cells, and led to the question of how energy from the electron transport chain was transmitted to the enzyme responsible for making ATP. No one seemed to have a satisfactory answer except Mitchell, who incorporated the general physical and chemical principles that had been established by previous scientists to propose the chemiosmotic theory.

Mitchell’s theory stated that the electron transport chain and ATP synthesis are embedded in the same membrane, that the membrane is impermeable to protons, that compounds involved in the electron transport chain and ATP synthesis are in contact with one another or the other side of the membrane, that there is an exchange of protons across the membrane, and finally that the electron transport chain and ATP synthesis are separated. The theory went against classical biology and biochemistry and infuriated some in the scientific community at the time, leading Mitchell to establish an independent research institute at Glynn House in Cornwall, where he and his long-term collaborator, Dr. Jennifer Moyle, worked to test his theory. Although it took years for his theory to gain acceptance, he was finally awarded the Nobel Prize in Chemistry in 1978.

For more information about Peter Mitchell and the Glynn Research Laboratory, please see the interview with Professor Rich and a recording of the full interview here.

Esther Cheng and Jillamika Pongsachai,
Biology majors, New York University

For further reading see:
1) ‘Peter Mitchell - Banquet Speech’. Nobelprize.org. Nobel Media AB 2014. Web. 9 Jun 2016 - http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1978/mitchell-speech.html
2) ‘Peter Mitchell - Biographical’. Nobelprize.org. Nobel Media AB 2014. Web. 9 Jun 2016 - http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1978/mitchell-bio.html
3) ‘Peter Mitchell - Nobel Lecture: David Keilin´s Respiratory Chain Concept and Its Chemiosmotic Consequences’. Nobelprize.org. Nobel Media AB 2014. Web. 9 Jun 2016 - http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1978/mitchell-lecture.html

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