After graduating, Hopkins then taught physiology and toxicology atGuy's Hospital from 1894 to 1898.[5] In 1898, while attending a meeting of thePhysiological Society, he was invited by Sir Michael Foster to join the Physiological Laboratory in Cambridge to investigate the chemical aspects of physiology.Biochemistry was not, at that time, recognised as a separate branch of science.[5] He was a lecturer in chemical physiology atEmmanuel College, Cambridge in March 1900, when he received the academic rankMaster of Arts (MA)honoris causa.[6] He earned a doctorate in physiology (D.Sc.) from theUniversity of London in July 1902,[7] and at the same time was given a readership in biochemistry at Trinity College.[8] While at Cambridge he was initiated intoFreemasonry.[9] In 1910 he became a Fellow of Trinity College, and an Honorary Fellow of Emmanuel College. In 1914 he was elected to the Chair of Biochemistry at Cambridge University, thus becoming the first Professor in that discipline at Cambridge.[10] His Cambridge students included neurochemistry pioneerJudah Hirsch Quastel and pioneerembryologistJoseph Needham.
Hopkins had for a long time studied how cells obtain energy via a complex metabolic process of oxidation and reduction reactions. His study in 1907 withSir Walter Morley Fletcher of the connection between lactic acid and muscle contraction was one of the central achievements of his work on the biochemistry of the cell.[5] He and Fletcher showed that oxygen depletion causes an accumulation of lactic acid in the muscle.[11] Their work paved the way for the later discovery byArchibald Hill andOtto Fritz Meyerhof that a carbohydrate metabolic cycle supplies the energy used for muscle contraction.[11]
In 1912 Hopkins published the work for which he is best known, demonstrating in a series of animal feeding experiments that diets consisting of pure proteins, carbohydrates, fats, minerals, and water fail to support animal growth. This led him to suggest the existence in normal diets of tiny quantities of as yet unidentified substances that are essential for animal growth and survival. These hypothetical substances he called "accessory food factors", later renamed vitamins.[12] It was this work that led his being awarded (together withChristiaan Eijkman) the 1929 Nobel Prize in Physiology or Medicine.[5]
DuringWorld War I, Hopkins continued his work on the nutritional value of vitamins. His efforts were especially valuable in a time of food shortages and rationing. He agreed to study the nutritional value of margarine and found that it was, as suspected, inferior to butter because it lacked the vitamins A and D. As a result of his work, vitamin-enriched margarine was introduced in 1926.[5]
Hopkins is credited with the discovery and characterisation in 1921 ofglutathione extracted from various animal tissues.[13] At the time he proposed that the compound was a dipeptide ofglutamic acid andcysteine. The structure was controversial for many years but in 1929 he concluded that it was a tripeptide ofglutamic acid,cysteine andglycine.[14] This conclusion agreed with that from the independent work ofEdward Calvin Kendall.[15]
Other significant honours were his election in 1905 as aFellow of the Royal Society (FRS), Great Britain's most prestigious scientific organisation; his knighthood by King George V in 1925; and the award in 1935 of theOrder of Merit, Great Britain's most exclusive civilian honour.
In 1898, he married Jessie Anne Stephens (1861–1937); they had one son and two daughters, the younger of whom,Jacquetta Hawkes, became a prominent archaeologist[18] and married the authorJ. B. Priestley.[19]
^Simoni, R. D.; Hill, R. L.; Vaughan, M. (2002). "On glutathione. II. A thermostable oxidation-reduction system (Hopkins, F. G., and Dixon, M. (1922) J. Biol. Chem. 54, 527–563)".The Journal of Biological Chemistry.277 (24): e13.PMID12055201.
