Peter Dennis Mitchell, FRS (29 September 1920 – 10 April 1992) was a

British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies. ** Britishness, the British identity and common culture * British English, ...

biochemist who was awarded the 1978

Nobel Prize for Chemistry ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...

for his discovery of the

chemiosmotic Chemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient. An important example is the formation of adenosine triphosphate (ATP) by the movement of hydrogen ions (H+) across a membra ...

mechanism of ATP synthesis.

Education and early life

Mitchell was born in

Mitcham Mitcham is an area within the London Borough of Merton in South London, England. It is centred southwest of Charing Cross. Originally a village in the county of Surrey, today it is mainly a residential suburb, and includes Mitcham Common. It h ...

, Surrey on 29 September 1920. His parents were Christopher Gibbs Mitchell, a civil servant, and Kate Beatrice Dorothy (née) Taplin. His uncle was Sir Godfrey Way Mitchell, chairman of

George Wimpey George Wimpey was a British construction firm. Formed in 1880 and based in Hammersmith, it initially operated largely as a road surfacing contractor. The business was acquired by Godfrey Mitchell in 1919, and he developed it into a constructi ...

. He was educated at

Queen's College, Taunton Queen's College is a co-educational independent school located in Taunton, the county town of Somerset, England. It is a day/boarding school for children aged 0–18. The school incorporates nursery, pre-prep, Prep, and senior schools. The curre ...

and

Jesus College, Cambridge Jesus College is a constituent college of the University of Cambridge. The college's full name is The College of the Blessed Virgin Mary, Saint John the Evangelist and the glorious Virgin Saint Radegund, near Cambridge. Its common name comes fr ...

where he studied the

Natural Sciences Natural science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer review and repeatab ...

Tripos At the University of Cambridge, a Tripos (, plural 'Triposes') is any of the examinations that qualify an undergraduate for a bachelor's degree or the courses taken by a student to prepare for these. For example, an undergraduate studying mathe ...

specialising in

Biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...

. He was appointed a research post in the Department of Biochemistry, Cambridge, in 1942, and was awarded a

Ph.D. A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is ...

in early 1951 for work on the mode of action of penicillin.

Career and research

In 1955 he was invited by Professor Michael Swann to set up a biochemical research unit, called the Chemical Biology Unit, in the Department of Zoology, at the

University of Edinburgh The University of Edinburgh ( sco, University o Edinburgh, gd, Oilthigh Dhùn Èideann; abbreviated as ''Edin.'' in post-nominals) is a public research university based in Edinburgh, Scotland. Granted a royal charter by King James VI in 15 ...

, where he was appointed a Senior Lecturer in 1961, then

Reader A reader is a person who reads. It may also refer to: Computing and technology * Adobe Reader (now Adobe Acrobat), a PDF reader * Bible Reader for Palm, a discontinued PDA application * A card reader, for extracting data from various forms of ...

in 1962, although institutional opposition to his work coupled with ill health led to his resignation in 1963. From 1963 to 1965, he supervised the restoration of a

Regency A regent (from Latin : ruling, governing) is a person appointed to govern a state '' pro tempore'' (Latin: 'for the time being') because the monarch is a minor, absent, incapacitated or unable to discharge the powers and duties of the monarchy ...

-fronted Mansion, known as Glynn House, at Cardinham near Bodmin,

Cornwall Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...

- adapting a major part of it for use as a research laboratory. He and his former research colleague, Jennifer Moyle founded a charitable company, known as Glynn Research Ltd., to promote fundamental biological research at Glynn House and they embarked on a programme of research on

reactions and reaction systems.

Chemiosmotic hypothesis

In the 1960s, ATP was known to be the energy currency of life, but the mechanism by which ATP was created in the mitochondria was assumed to be by substrate-level phosphorylation. Mitchell's chemiosmotic hypothesis was the basis for understanding the actual process of oxidative phosphorylation. At the time, the biochemical mechanism of ATP synthesis by oxidative phosphorylation was unknown. Mitchell realised that the movement of ions across an

electrochemical potential In electrochemistry, the electrochemical potential (ECP), ', is a thermodynamic measure of chemical potential that does not omit the energy contribution of electrostatics. Electrochemical potential is expressed in the unit of J/ mol. Introductio ...

difference could provide the energy needed to produce ATP. His hypothesis was derived from information that was well known in the 1960s. He knew that living cells had a membrane potential; interior negative to the environment. The movement of charged ions across a membrane is thus affected by the electrical forces (the attraction of positive to negative charges). Their movement is also affected by thermodynamic forces, the tendency of substances to

diffuse Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

from regions of higher concentration. He went on to show that ATP synthesis was coupled to this

electrochemical gradient An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and ...

. 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; and by the discovery by André Jagendorf that a pH difference across the

thylakoid Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thyl ...

membrane in the chloroplast results in ATP synthesis.

Protonmotive Q-cycle

Later, Peter Mitchell also hypothesized some of the complex details of electron transport chains. He conceived of the coupling of proton pumping to quinone-based electron bifurcation, which contributes to the proton motive force and thus, ATP synthesis.

Awards and honours

In 1978 he was awarded the

Nobel Prize in Chemistry ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...

"for his contribution to the understanding of biological energy transfer through the formulation of the chemiosmotic theory."} including the Nobel Lecture on 8 December 1978 ''David Keilin’s Respiratory Chain Concept and Its Chemiosmotic Consequences'' He was elected a Fellow of the Royal Society (FRS) in 1974.

References

External links

* {{DEFAULTSORT:Mitchell, Peter D 1920 births 1992 deaths People from Mitcham English biochemists Alumni of Jesus College, Cambridge British biochemists Nobel laureates in Chemistry People educated at Queen's College, Taunton British Nobel laureates Recipients of the Copley Medal Academics of the University of Edinburgh Fellows of the Royal Society Foreign associates of the National Academy of Sciences English Nobel laureates Independent scholars Scientists from Cornwall