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5.4 outline the evidence provided by: Hill and Scarisbruck Ruben to confirm that the oxygen released by photosynthesis originated from water
outline the evidence provided by:
- Hill and Scarisbruck
- Ruben
to confirm that the oxygen released by photosynthesis originated from water
- Hill and Scarisbrick in 1939, shone light on chloroplast preparations in the absence of carbon dioxide. They supplied the chloroplasts with salts of ferric iron such as ferricyanide or ferrioxalate to accept the hydrogen instead of carbon dioxide. The equation for the reaction, known as the Hill reaction, is
2H2O + 4[Fe(CN)6]3- → 4[Fe(CN)6]4- + 4H+ + O2
- Despite the fact that Hill and Scarisbrick were not able to show that carbon dioxide received the hydrogen, they proved that oxygen was given off in the absence of CO2 and came from water. This suggested that CO2 fixation and O2 evolution are separate processes.
- In 1940 Sam Ruben used an isotope of oxygen, 18O to find out where the oxygen atoms went in photosynthesis. Ruben fed plants water containing 18O but because 18O is not a radioactive isotope of the most common form of oxygen, 16O, Ruben used a mass spectrometer to determine the fate of the 18O. The 18O was found in the oxygen gas produced by the plant and none in the glucose formed.
Photosynthesis: Electron flow and the Hill reaction
, Vanderbilt University, Nashville, Tennessee, USA.