After graduating, Hopkins then taught physiology and toxicology at
Guy's Hospital from 1894 to 1898. He earned a doctorate in physiology (D.Sc.) from the
University of London in July 1902, and at the same time was given a readership in biochemistry at Trinity College. While at Cambridge he was initiated into
Freemasonry. 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. His Cambridge students included neurochemistry pioneer
Judah Hirsch Quastel and pioneer
embryologist Joseph 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 with
Sir 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. 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. It was this work that led his being awarded (together with
Christiaan Eijkman) the 1929 Nobel Prize in Physiology or Medicine. At the time he proposed that the compound was a dipeptide of
glutamic acid and
cysteine. The structure was controversial for many years but in 1929 he concluded that it was a tripeptide of
glutamic acid,
cysteine and
glycine. This conclusion agreed with that from the independent work of
Edward Calvin Kendall. == Awards and honours ==