Portrait of Sir Arthur Harden (1865-1940), English biochemist and Nobel Laureate. Harden obtained his degree from Manchester, before studying for his doctorate in Germany. In 1897 he joined the Jenner Institute, and in 1904 began work on alcoholic fermentation. He was the first to demonstrate that yeast consisted of two parts, a protein enzyme and a small molecular companion. This he termed a coenzyme, showing that it was not itself a protein but was vital to the action of the enzyme. This led to an understanding of the importance of many vitamins and trace elements, and Harden shared the 1929 Nobel Prize for Chemistry with Euler-Chelpin as a result. Harden was knighted in 1936.