Back Home

4.1 describe and discuss the importance of Van Neil’s hypothesis that water was the source of oxygen given out in photosynthesis

describe and discuss the importance of Van Niel’s hypothesis that water was the source of oxygen given out in photosynthesis

CO2 + 2H2S → CH2O + H2O + 2S

CO2 + 2H2O → CH2O + H2O + O2

The importance of van Niel’s hypothesis is that it gave one of the first clues to the mechanism of photosynthesis. Prior to Van Niel’s work, scientists had thought that carbon dioxide was split, the oxygen released and the C added to water to make glucose. Van Niel’s hypothesis that water is split to produce oxygen was later proved using radioactive oxygen – 18. Water labeled with 18O produced oxygen gas labeled with 18O. When CO2 labeled with 18O was used, the radioactivity was detected in the glucose and water, not the oxygen gas produced.