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Anne Marie Helmenstine, Ph.D.

This Day in Science History - January 8 - Melvin Calvin and Dark Reactions

By January 7, 2014

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January 8th marks the passing of Melvin Calvin. Calvin was an American biochemist who discovered what would become referred to as the "Calvin cycle" or carbon fixation in photosynthesis. The Calvin cycle deals with the part of photosynthesis that is called dark reactions. A more accurate description would be light-independent reactions. These reactions don't require light to progress like most photosynthesis reactions and can occur either day or night. They take place in the stroma of the chloroplast and convert carbon dioxide into sugar using ATP and NADPH.

Calvin used radioactive carbon-14 to trace the path of carbon during this cycle to discover important parts of photosynthesis. He discovered the previous belief that sunlight acts on carbon dioxide to fuel the process was incorrect. It was the action of sunlight on the chlorophyll that drove the reactions. His work mapping the path of carbon through all the reactions involved in photosynthesis earned him the 1961 Nobel Prize in Chemistry.

Find out more about photosynthesis and what else occurred on this day in science history.


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