Hill, Robert (1899-1991)

British biochemist who showed that during photosynthesis, oxygen is produced, and that this derived oxygen comes from water. This process is now known as the Hill reaction. He also demonstrated the evolution of oxygen in human blood cells by the conversion of haemoglobin to oxyhaemoglobin. Hill was educated at Cambridge and remained researching there until 1938. From 1943 to 1966 he was a member of the scientific staff of the Agricultural Research Council. The process of photosynthesis has been shown to occur in two separate sets of reactions, those that require sunlight (the light reactions) and those that do not (the dark reactions). Both sets of reactions are dependent on one another. In the light reactions some of the energy of sunlight is trapped within the plant and in the dark reactions this energy is used to produce potentially energy-generating chemicals, such as sugar. Hill's experiments in 1937 confirmed that the light reactions of photosynthesis occur within the chloroplasts of leaves, as well as elucidating in part the mechanism of the light reactions. To do this, he isolated chloroplasts from leaves and then illuminated them in the presence of an artificial electron-acceptor.