The Calvin Cycle

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The Calvin Cycle

• Named after Melvin Calvin (1911-1997)

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The Calvin Cycle Carbon atoms from CO2 are
bonded or fixed into organic molecules Carbon
Fixation the incorporation of CO2 into organic
molecules
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Step1 of 3 in the Calvin cycleCO2 enters
through the stoma, diffuses into cytosol then it
enters the stroma of the chloroplast.Enzyme
combines CO2 with a five carbon compound RuBP
This produces a six carbon compound This
Splits into a pair of three carbon compounds PGA
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Step 2 PGA is converted into another three-
carbon molecule called PGAL. PGA receives a
phosphate from ATP then the resulting compound
receives a proton from NADPH this causes the
received phosphate to be released producing
PGAL The ending products are NADP and ADP
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Step 3 PGAL is converted back into RuBP This
step requires ATP which is changed to ADP This
step allows the Calvin cycle to continue Some
PGAL Molecules are not converted into RuBP but
they leave the cycle and make organic compounds
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C3 Pathway

• All Plants that fix carbon using the Calvin Cycle
  are C3 Plants
• Low CO2 or high O2 will slow the Calvin Cycle
• When the Stoma is closed there will be less CO2
• When Photosynthesis is running it makes O2

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C4 Pathway

• Fixes a four carbon molecule
• Corn, Sugar cane and Crabgrass (monocots)

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CAM Pathway

• Stands for Crassulacean Acid Metabolism
• Plants that live in arid environments
• Cactuses, and pineapple