Bloch, Konrad (Emil) (1912–2000)

German-born US chemist who was awarded a Nobel Prize for Physiology or Medicine in 1964, together with his collaborator in Germany, Feodor Lynen, for work on cholesterol and fatty-acid metabolism. Making use of the radioisotope carbon-14 (the radioactive form of carbon), Bloch was able to follow the complex steps by which the body chemically transforms ethanoic (acetic) acid into cholesterol.

Bloch was born in Neisse (now Nysa, Poland) and graduated as a chemical engineer from Munich Technische Hochschule. He emigrated to the USA in 1936 and studied biochemistry at Columbia University. In 1954 he became a professor at Harvard.

Bloch demonstrated that carbon atoms of carbon-labelled ethanoate (acetate) fed to rats was incorporated into cholesterol in the animals' livers. Using ethanoic (acetic) acid labelled with deuterium he showed for the first time that this acid, a compound having only two carbon atoms, is the major precursor of cholesterol. This discovery was the first of a long series that elucidated the biological synthesis of the steroid.