Answer :
Final answer:
Carbon dioxide joins with a 5-carbon molecule called RuBP in the Calvin cycle.
Explanation:
When carbon dioxide enters the Calvin cycle, it combines with a 5-carbon molecule called RuBP (ribulose-1,5-bisphosphate). This reaction is catalyzed by the enzyme RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase). The resulting unstable compound quickly breaks down into two molecules of 3-phosphoglycerate (3-PGA).
Learn more about RuBP as a molecule in the Calvin cycle here:
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