Peter Mitchell

1. Peter Mitchell and the Chemiosmotic Theory

2. Who is Peter Mitchell? Was born 29th September, 1920 and died 10thApril 1992. Was a British biochemist and a Fellow of the Royal Society. He went to  Queen's College, Taunton, and  Jesus College, Cambridge where he studied the Natural Sciences and specialized in biochemistry. In 1978 he won the Nobel Prize in Chemistry “for his contribution to the understanding of biological energy transfer through the formulation of the chemiosmotic theory.”

3. What We Know So Far… • In 1945, Albert Lehninger established the existence of a link between the Krebs cycle and the catabolism of fatty acids In he cell. • In 1949, Morris Friedkin, together with his PhD supervisor,  Albert Lehninger , showed the existence of a connection between different metabolic pathways for coenzyme NADH to oxygen as a source of energy in oxidative phosphorylation.

4. The Experiment • Hypothesis: the ATP created by the ATP synthase when H+ protons are pumped back into the matrix is made through oxidative phosphorylation, not substrate-level phosphorylation. • Mitchell studied the mitochondrion, and was able to determine how the different enzymes involved in the conversion of ADP to ATP are distributed within the membranes that partition its interior. He showed how these enzymes' arrangement facilitates their use of H+ ions as an energy source in the conversion of ADP to ATP.

5. Findings and Discovery • Mitchell realized that the movement of ions across an electrochemical membrane potential could provide the energy needed to produce ATP. He knew that living cells hadmembranes, and that the movement of charged ions across a membrane is thus affected by the electrical forces. Their movement is also affected by thermodynamic forces, the tendency of substances to diffuse from regions of higher concentration. He went on to show that ATP synthesis was related to this electrochemical gradient. • His hypothesis was confirmed by the discovery of ATP synthase, a membrane-bound protein that uses the potential energy of the electrochemical gradient to make ATP.

6. In The End… • This theory was first received with scepticism; but, was later accepted once work in both Mitchell's and many other laboratories showed that the basic postulates of his theory were correct. The chemiosmotic theory is now generally accepted as a fundamental principle in bioenergetics and now provides a rational basis for future work on the detailed mechanisms of oxidative phosphorylation and photophosphorylation. • The Nobel Prize for Chemistry in 1978, awarded to Peter Mitchell as the sole recipient, recognized his predominant contribution towards establishing the validity of the chemiosmotic hypothesis, and ipso facto, the long struggle to convince an initially hostile establishment.

7. References • Wikipedia, . "Peter D. Mitchell."Wikipedia. Wikimedia Foundation, Inc., 24th September 2011. Web. 23 Oct 2011. <http://en.wikipedia.org/wiki/Peter_D._Mitchell>. • Crofts, Anthony. "Peter Mitchell and The Chemiosmotic Hypothesis."Life Sciences -University of Illinois at Urbana-Champaign. University of Illinois at Urbana-Champaign, 1996. Web. 23 Oct 2011. http://www.life.illinois.edu/crofts/bioph354/mitchell.html • "Functions of NAD (Nicotinamide adenine dinucleotide) ."Nangluongsinhhoc. Blogger, 2011. Web. 23 Oct 2011. <http://nangluongsinhhoc2011.blogspot.com/2011/04/functions-of-nad-nicotinamide-adenine.html>. • "Press Release: The 1978 Nobel Prize in Chemistry". Nobelprize.org. 24 Oct 2011. http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1978/press.html