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Photosynthesis: Dark Reactions

Submitted by mpetracchi on Thu, 11/07/2019 - 00:36

After a plant has taken in sunlight and water to produce ATP and NADPH, it has the necessary ingredients to produce a sugar molecule. First, a plant must take in CO2 to be fixed using the 5 carbon molecule Rubisco or RuBP. Carbon fixing is the process by which gaseous carbon is converted to a non-gaseous molecule. Exactly 3 CO2's and 3 RuBP's are used to produce 6 3-PGA's. The 6 3-PGA's are then are reduced using 6 ATP's and 6 NADPH's into 6 G3P molecules. One of these G3P molecules is set aside as a sugar product and the remaining 5 are used to regenerate RuBP. The product, G3P, is composed of 3 carbons, oxygen, hydrogen, and phosphorus. Regenerating RuBP requires an additional 3 ATP and the 5 leftover G3P's. Once RuBP has been regenerated it can be used to fix more CO2 and continue the dark reaction cycle.

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