The Calvin Cycle
By: MJ Pineda
The Calvin Cycle is basically a part of photosynthesis where plants take in carbon dioxide and uses ATP and NADPH to make sugars from the CO2 and water for the plant to use or for animals to eat. It does not require light, and is interestingly called the "dark cycle" 1.
The first step of this cycle consists of A carbon atom from carbon dioxide molecule will enter the cycle and joins with a five carbon molecule that is present.
The six carbon molecule that results from that compound breaks up into two molecules, each with three carbon atoms.
As the reactions in the cycle continue, ATP is dephosphorylated (loses a phosphate) to ADP. The energy that is released is used to raise the energy of the molecules reacting in the cycle.
Further energy is supplied by the oxidation of NADPH to NADP.
A carbon atom breaks off and is available to be used to make G3P, a high energy molecule that has three carbons. The bonds connecting this carbon atom to hydrogen and carbon are much higher in energy than the original C-O bonds of carbon dioxide. This carbon is left behind as the cycle continues. G3P has three carbons, so it will require three turns of the cycle to provide the necessary carbons to make one molecule of G3P. Since glucose has six carbons, it will take two G3Ps or six turns of the cycle to make one molecule of glucose.
The five carbons that remain combine and continue in the cycle. Another ATP is dephosphorylated to ADP to provide the necessary energy.
The cycle repeats continuously, each time making a carbon atom available for G3P. When three cycles are completed, one G3P can be removed for making glucose and other organic molecules.
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